#include <cstdio>
#include <cmath>
int main()
{
    long double a, b;
    scanf("%Lf %Lf", &a, &b);
    for (long double r = 0; r < b; r += 0.0001)
    {
        if ((b * floor(a / b) + r) == a)
        {
            printf("%Lf", r);
            return 0;
        }
    }
    return 0;
}