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