Contract Source Code:

pragma solidity ^0.4.25;

library SafeMath {
    function mul(uint256 a, uint256 b) internal pure returns (uint256 c) {
        if (a == 0) {
            return 0;
        }
        c = a * b;
        assert(c / a == b);
        return c;
    }
    function div(uint256 a, uint256 b) internal pure returns (uint256) {
        return a / b;
    }
    function sub(uint256 a, uint256 b) internal pure returns (uint256) {
        assert(b <= a);
        return a - b;
    }
    function add(uint256 a, uint256 b) internal pure returns (uint256 c) {
        c = a + b;
        assert(c >= a);
        return c;
    }
}
contract ForeignToken {
    function balanceOf(address _owner) constant public returns (uint256);
    function transfer(address _to, uint256 _value) public returns (bool);
}
contract ERC20Basic {
    uint256 public totalSupply;
    function balanceOf(address who) public constant returns (uint256);
    function transfer(address to, uint256 value) public returns (bool);
    event Transfer(address indexed from, address indexed to, uint256 value);
}
contract ERC20 is ERC20Basic {
    function allowance(address owner, address spender) public constant returns (uint256);
    function transferFrom(address from, address to, uint256 value) public returns (bool);
    function approve(address spender, uint256 value) public returns (bool);
    event Approval(address indexed owner, address indexed spender, uint256 value);
}
contract DiamondRealEstate is ERC20 {
    using SafeMath for uint256;
    address owner = msg.sender;
    mapping (address => uint256) balances;
    mapping (address => mapping (address => uint256)) allowed;
    string public constant name = 'Diamond Real Estate';
    string public constant symbol = 'DRE';
    uint public constant decimals = 18;
    uint256 public totalSupply = 15000000000e18;
    uint256 public totalDistributed =  3000000000e18;    
    uint256 public constant MIN_CONTRIBUTION = 1 ether / 100;
    uint256 public tokensPerEth = 20000000e18;
    event Transfer(address indexed _from, address indexed _to, uint256 _value);
    event Approval(address indexed _owner, address indexed _spender, uint256 _value);
    event Distr(address indexed to, uint256 amount);
    event DistrFinished();
    event Airdrop(address indexed _owner, uint _amount, uint _balance);
    event TokensPerEthUpdated(uint _tokensPerEth);
    event Burn(address indexed burner, uint256 value);
    bool public distributionFinished = false;
    modifier canDistr() {
        require(!distributionFinished);
        _;
    }
    modifier onlyOwner() {
        require(msg.sender == owner);
        _;
    }
    constructor () public {
        owner = msg.sender;
        distr(owner, totalDistributed);
    }
    function transferOwnership(address newOwner) onlyOwner public {
        if (newOwner != address(0)) {
            owner = newOwner;
        }
    }
    function finishDistribution() onlyOwner canDistr public returns (bool) {
        distributionFinished = true;
        emit DistrFinished();
        return true;
    }
    function distr(address _to, uint256 _amount) canDistr private returns (bool) {
        totalDistributed = totalDistributed.add(_amount);        
        balances[_to] = balances[_to].add(_amount);
        emit Distr(_to, _amount);
        emit Transfer(address(0), _to, _amount);
        return true;
    }
    function doAirdrop(address _participant, uint _amount) internal {
        require(_amount > 0);      
        require(totalDistributed < totalSupply);
        balances[_participant] = balances[_participant].add(_amount);
        totalDistributed = totalDistributed.add(_amount);
        if (totalDistributed >= totalSupply) {
            distributionFinished = true;
        }
        emit Airdrop(_participant, _amount, balances[_participant]);
        emit Transfer(address(0), _participant, _amount);
    }
    function adminClaimAirdrop(address _participant, uint _amount) public onlyOwner {        
        doAirdrop(_participant, _amount);
    }
    function adminClaimAirdropMultiple(address[] _addresses, uint _amount) public onlyOwner {        
        for (uint i = 0; i < _addresses.length; i++) doAirdrop(_addresses[i], _amount);
    }
    function updateTokensPerEth(uint _tokensPerEth) public onlyOwner {        
        tokensPerEth = _tokensPerEth;
        emit TokensPerEthUpdated(_tokensPerEth);
    }
    function () external payable {
        getTokens();
    }
    function getTokens() payable canDistr  public {
        uint256 tokens = 0;
        uint256 bonus = 0;
        require(msg.value >= MIN_CONTRIBUTION);
        require(msg.value > 0);
        tokens = tokensPerEth.mul(msg.value) / 1 ether;        
        address investor = msg.sender;
        if (msg.value >= 0.5 ether) {
            bonus = (tokens * 10) / 100;
        }
        if (msg.value >= 1 ether) {
            bonus = (tokens * 20) / 100;
        }
        if (msg.value >= 4 ether) {
            bonus = (tokens * 30) / 100;
        }
        if (tokens > 0) {
            distr(investor, (tokens + bonus));
        }
        if (totalDistributed >= totalSupply) {
            distributionFinished = true;
        }
    }
    function balanceOf(address _owner) constant public returns (uint256) {
        return balances[_owner];
    }
    modifier onlyPayloadSize(uint size) {
        assert(msg.data.length >= size + 4);
        _;
    }
    function transfer(address _to, uint256 _amount) onlyPayloadSize(2 * 32) public returns (bool success) {
        require(_to != address(0));
        require(_amount <= balances[msg.sender]);
        balances[msg.sender] = balances[msg.sender].sub(_amount);
        balances[_to] = balances[_to].add(_amount);
        emit Transfer(msg.sender, _to, _amount);
        return true;
    }
    function transferFrom(address _from, address _to, uint256 _amount) onlyPayloadSize(3 * 32) public returns (bool success) {
        require(_to != address(0));
        require(_amount <= balances[_from]);
        require(_amount <= allowed[_from][msg.sender]);
        balances[_from] = balances[_from].sub(_amount);
        allowed[_from][msg.sender] = allowed[_from][msg.sender].sub(_amount);
        balances[_to] = balances[_to].add(_amount);
        emit Transfer(_from, _to, _amount);
        return true;
    }
    function approve(address _spender, uint256 _value) public returns (bool success) {
        if (_value != 0 && allowed[msg.sender][_spender] != 0) { return false; }
        allowed[msg.sender][_spender] = _value;
        emit Approval(msg.sender, _spender, _value);
        return true;
    }
    function allowance(address _owner, address _spender) constant public returns (uint256) {
        return allowed[_owner][_spender];
    }
    function getTokenBalance(address tokenAddress, address who) constant public returns (uint){
        ForeignToken t = ForeignToken(tokenAddress);
        uint bal = t.balanceOf(who);
        return bal;
    }
    function withdraw() onlyOwner public {
        address myAddress = this;
        uint256 etherBalance = myAddress.balance;
        owner.transfer(etherBalance);
    }
    function burn(uint256 _value) onlyOwner public {
        require(_value <= balances[msg.sender]);
        address burner = msg.sender;
        balances[burner] = balances[burner].sub(_value);
        totalSupply = totalSupply.sub(_value);
        totalDistributed = totalDistributed.sub(_value);
        emit Burn(burner, _value);
    }
    function withdrawForeignTokens(address _tokenContract) onlyOwner public returns (bool) {
        ForeignToken token = ForeignToken(_tokenContract);
        uint256 amount = token.balanceOf(address(this));
        return token.transfer(owner, amount);
    }
}