'use strict';

function Main(input) {
    let S = input.trim().split(' ');
    const A = BigInt(S[0]);
    const B = BigInt(S[1].replace('.', ''));
    // console.log(S)
    // console.log(A, B)

    const result = A * B / BigInt(100)

    console.log(String(result).replace('n', ''));

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