"use strict";
var input = require("fs").readFileSync("/dev/stdin", "utf8");
var cin = input.trim().split(/ |\n/), cid = 0;

console.log(main().toString());

function main() {
    var a = BigInt(cin.shift());
    var b = BigInt(Math.round((+cin.shift()) * 100));
    return a * b / 100n;
}