#include <stdio.h>
#include <inttypes.h>

int main(void) {
	uint64_t A;
	uint64_t B1, B2;
	if(scanf("%" SCNu64 "%" SCNu64 ".%" SCNu64, &A, &B1, &B2) != 3) return 1;
	printf("%" PRIu64 "\n", A * (B1 * 100 + B2) / 100);
	return 0;
}
