"use strict";

const main = arg => {
    const input = arg.trim().split("\n");

    const a = BigInt(input[0].split(" ")[0]);
    const b = BigInt(parseFloat(input[0].split(" ")[1])*100);
    console.log(Number(a*b/100n))
}
main(require('fs').readFileSync('/dev/stdin', 'utf8'));  