#include <stdio.h>

int main (void) {

    long long a;
    double b;

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

    int integerB = (int) ((b+0.005) * (double)100);

    long long result = a * integerB;

    printf("%lld\n", result / 100);

    return 0;
}