contract ERC20 {
  uint256 public totalSupply;
  function balanceOf(address who) public view returns (uint256);
  function transfer(address to, uint256 value) public returns (bool); //real elf
  //function transfer(address _to, uint256 _value) public;
  function allowance(address owner, address spender) public view returns (uint256);
  function transferFrom(address from, address to, uint256 value) public returns (bool);
  function approve(address spender, uint256 value) public returns (bool);
  //function burnTokens(uint256 _amount) public returns (bool);
  event Transfer(address indexed from, address indexed to, uint256 value);
  event Approval(address indexed owner, address indexed spender, uint256 value);
}
function allowance(address owner, address spender) public view returns (uint256);

//real elf
//function transfer(address _to, uint256 _value) public;