#include <stdio.h>

int main(void) {
	unsigned long long a = 0;
	double b = 0;
	unsigned long long c = 0;

	scanf("%llu", &a);
	scanf("%lf", &b);

	c =(unsigned long long)( b * 100);

	a = (c * a) / 100;
	
	printf("%llu", a);

	return 0;
}