function main(lines) {
  let [A, B] = lines[0].split(' ');
  A = BigInt(A);
  B = B;

  const res = A * BigInt(B.replace('.', '')) / BigInt(100);

  console.log(res.toString());
}


main( require("fs").readFileSync("/dev/stdin", "utf8").trim().split("\n") );



function splitN(s) {
  return s.split(' ').map(Number);
}