#include <bits/stdc++.h>
using namespace std;
long long int power(long long int x, long long int y) {
  long long int res = 1;
  x = x;
  if (y == 0) return 1;
  if (x == 0) return 0;
  while (y > 0) {
    if (y & 1) res = (res * x);
    y = y >> 1;
    x = (x * x);
  }
  return res;
}
void solve() {
  long long int a, b;
  cin >> a >> b;
  char c;
  cin >> c;
  int d;
  cin >> d;
  b *= 100;
  b += d;
  cout << a * b / 100 << endl;
  return;
}
int main() { solve(); }
