'use strict';

function Main(input) {
    let S = input.trim().split(' ');
    const A = BigInt(S[0]);
    const B = BigInt(Math.floor(S[1] * 100));
    // console.log(S)
    // console.log(A, B)

    const result = Number(A * B / 100n);

    console.log(result);

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

// Main(`198 1.10`);
// Main(`1 0.01`);
// Main(`1000000000000000 9.99`);