#include <stdio.h>

int main(){
  
    long long a, b, c;
    
    scanf("%lld %lld.%lld", &a, &b, &c);
    
    long long d = b * 100 + c;
    long long x = (a * d) / 100;
  
    printf("%lld", x);
    
    return 0;
}