uva 10375 - Choose and divide

#include <cstdio>int main(){    int p, q, r, s;    while (~scanf("%d %d %d %d", &p, &q, &r, &s))    {        if (p - q < q) q = p - q;        if (r - s < s) s = r - s;        double ret = 1.0;        for (int i = 1; i <= q || i <= s; ++i)        {            if (i <= q) ret = ret * (p - q + i) / i;            if (i <= s) ret = ret / (r - s + i) * i;        }        printf("%.05lf\n", ret);    }    return 0;}