#include <stdio.h>

int main () {
    long A;
    double B;
    scanf("%ld", &A);
    scanf("%lf", &B);

    //long seisu = (long) B;
    //long shosu = (long) (((double)(B - seisu)) * 100);

    //printf("%ld . %ld\n", seisu, shosu);
    //long ans;
    //ans += A * seisu + ((A * shosu) / 100);
    printf("%ld\n", (long)(A * B));

    return 0;
}
