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Breakpoint-remixing.sol

pragma solidity ^0.4.23;

contract BreakpointSample {
    address public owner;
    uint256 public blockNumberToUnlock;
    
    constructor (address _owner, uint256 blocksToUnlock) public {
        if (_owner == address(0)) {
            owner = msg.sender;
        } else {
            owner = _owner;
        }
        require(blocksToUnlock > 0);
        owner = msg.sender;
        blockNumberToUnlock = block.number + blocksToUnlock;
    }
    
    function changeOwner(address newOwner) external {
        require(msg.sender == owner);
        owner = newOwner;
    }
    
    function sendBack() external {
        require(block.number > blockNumberToUnlock);
        
        owner.transfer(address(this).balance);
    }
    
    function () payable public {
        
    }
}