interface  ptopinterface  {
       //new exchange function
       function newExchange (address smart1, uint256 amount1, address two2, address smart2, uint256 amount2) external payable returns(uint exchangeId);
       //new exchange event
       event NewExchange (uint exchangeId, address one1, address indexed smart1, uint256 amount1, address two2, address indexed smart2, uint256 amount2);
      //get the exchange details
       function getExchange (uint _Id) external view returns (address _one1,address _smart1,uint256 _amount1, address _two2, address _smart2, uint256 _amount2, bool); 
       //cancek an exchange by one of the parties
       function cancelExchange (uint exchangeId) external payable returns (bool success);
       //cancel exchange event
       event CancelExchange (uint exchangeId);
       // do exchange function
       function doExchange (uint exchangeId) external payable returns (bool success);
       //do exchange event
       event DoExchange (uint exchangeId);
    
}
function doExchange (uint exchangeId) external payable returns (bool success);
// do exchange function