#include <stdio.h>
int main(void){
	long a;
	// long double b;
	// scanf("%ld", &a);
	// scanf("%Lf", &b);
	// printf("%ld\n", (long)(a*b));
	char b[5];
	scanf("%ld", &a);
	scanf("%s", b);
	long long_b = (b[0]-'0')*100 + (b[2]-'0')*10 + (b[3]-'0');
	printf("%ld\n", a*long_b/100);
	return 0;
}