#include <stdio.h>

#define rep(i, n) for (int i = 0; i < n; i = i + 1)
#define MAX 10010
#define MAX_INT 9223372036854775807

int main() {
  long long A;
  double B;
  scanf("%lld%lf", &A, &B);
  long long i_B = (long long)(B * 100);

  double output;
  long long temp_output;
  temp_output = A * i_B;
  output = temp_output / 100;

  printf("%lld\n", (long long)output);
  return 0;
}
