#include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
using ll = long long;
using vi = vector<int>;
using vvi = vector<vi>;
int main() {
  int64_t a;
  long double b;
  cin >> a >> b;
  int64_t ans = (int64_t)a*b;
  cout << ans << endl;
}
