#include <stdio.h>

int main(void){
  double a, b, c;
  int d;
  scanf("%lf %lf", &a, &b);
  c = a * b * 100;
  d = (int)c % 100;
  c = c - (double)d;
  c /= 100;

  printf("%.f\n", c);

  return 0;
}