#include <stdio.h>

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

	scanf("%llu", &a);
	scanf("%lf", &b);
	aa = b * 1000;

	c = aa % 100;
	if (c >= 5) {
		c = aa / 100 + 1;
	}
	else if (c < 5) {
		c = aa / 100;
	}

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

	return 0;
}
