"use strict";

const main = arg => {
    const inputList = arg.trim().split("\n");
    // 回答を記述
    const A = BigInt(inputList[0].split(" ")[0]);
    const B = inputList[0].split(" ")[1]
    const num = A * BigInt(parseInt(B.replace(".", ""))) / 100n;
    console.log(num.toString());
}

main(require('fs').readFileSync('/dev/stdin', 'utf8'));