process.stdin.resume();
process.stdin.setEncoding('utf8');

let inputData = '';
let a, b;

process.stdin.on('data', inputStdin => {
  inputData += inputStdin;
});

process.stdin.on('end', _ => {
  inputData = inputData.replace(/\s*$/g, '')
    .split(' ');
  main();
});

function solve() {
  return a * b / 100n;
}

function main() {
  a = BigInt(inputData[0]);
  b = BigInt(Math.floor(inputData[1] * 100));

  process.stdout.write(solve().toString());
}
