#include <stdio.h>
 
int main(void)
{
  long long a, r;
  double b;
  
  scanf("%lld", &a);
  scanf("%lf", &b);
  
  b = b * 100;
  
  r = (long long)(a * b);
  
  r /= 100;
  
  printf("%lld", r);
  
  return 0;
}