'use strict';

const main = arg => {
    const input = arg.trim();
 
    const a = BigInt(input[0].split(' ')[0]);
    const b = BigInt(input[0].split(' ')[1].replace('.', ''));
    let ret = a*b/BigInt(100)
    console.log(String(ret).replace('n', ''));
}
main(require('fs').readFileSync('/dev/stdin', 'utf8'));  