interface IConverter {
    function token() external returns (address _share);
    function convert(address _input, address _output, uint _inputAmount) external returns (uint _outputAmount);
    function convert_rate(address _input, address _output, uint _inputAmount) external view returns (uint _outputAmount);
    function convert_stables(uint[3] calldata amounts) external returns (uint _shareAmount); // 0: DAI, 1: USDC, 2: USDT
    function get_dy(int128 i, int128 j, uint dx) external view returns (uint);
    function exchange(int128 i, int128 j, uint dx, uint min_dy) external returns (uint dy);
    function calc_token_amount(uint[3] calldata amounts, bool deposit) external view returns (uint _shareAmount);
    function calc_token_amount_withdraw(uint _shares, address _output) external view returns (uint _outputAmount);
}
function get_dy(int128 i, int128 j, uint dx) external view returns (uint);
// 0: DAI, 1: USDC, 2: USDT