#include <stdio.h>

int main(){
	unsigned long long a;
	unsigned long long b_integer, b_decimal;

	scanf("%llu%llu%*c%llu", &a, &b_integer, &b_decimal);

	unsigned long long b_times_100 = b_integer * 100 + b_decimal;

	printf("%llu\n", a * b_times_100 / 100);

}
