interface ERC20 {
    function approve(address,uint) external returns (bool);
    function balanceOf(address) external view returns (uint);
    function mint(address,uint) external; // only on src chain
    function burn(uint) external; // only on src chain
    function Swapout(uint,address) external returns (bool);
    function transfer(address,uint) external returns (bool);
}
function burn(uint) external;
// only on src chain