#include <stdio.h>
#include <stdlib.h>
 
int main(void) {
	unsigned long long A;
	char B[5];
	char C[4];
	int t;
	
	scanf("%lld", &A);
	scanf("%s", B);
	
	C[0] = B[0];
	C[1] = B[2];
	C[2] = B[3];
	C[3] = B[4];
		
	t = atoi(C);
	
	printf("%lld\n", (long long)((A * t)/ 100));
	
	return 0;
}
