#include <stdio.h>
#include <string.h>
#include <stdlib.h>

int main(void){
unsigned long long A;
char B[100];
scanf("%llu %s", &A, B);
size_t l = strlen(B);
B[l-3] = B[l-2]; B[l-2] = B[l-1]; B[l-1] = '\0';
unsigned long long ans = A * atoll(B);
printf("%llu", ans / 100);
return 0;
}