const main = arg => {
    let input = arg.trim();

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