#include <stdio.h>
#include <stdlib.h>
#include <string.h>

int main(void)
{
    long long A;
    long long ans;
    double B;
    int tB;
    long long tA;
    scanf("%lld", &A);
    scanf("%lf", &B);
    tA = (long long)(A / 100);
    tB = (int)(B * 100);
    ans = tA * tB + ((A - tA * 100) * B) / 100;
    printf("%lld", ans);
    return 0;
}