Hi, I just took part in Codeforces Round #105 Div2 . I submitted a solution for problem D which failed on the first pretest. After the contest, I checked why my program had failed and found out that the answer that the judge received from my program and that which I received on my system were different for the same input! I am sure my code is correct but yet the judge receives a different output from it. Can someone tell me why this is happening. Below is my code (submission id — 1143031) :

long double A[1003][1003];

long double prob(long double b, long double w) {

if(w <= 0)
    return 0;

if(b==1)
    return (w/(w+b));

if(b <= 0)
    return 1;

if(A[(int)b][(int)w] != -1)
    return A[(int)b][(int)w];

long double ans = w/(w+b) + (b/(w+b))*(b-1)/(w+b-1)*( (w/(w+b-2))*prob(b-2, w-1) + ( (b-2)/(w+b-2) )*prob(b-3, w));
A[(int)b][(int)w] = ans;
return ans;

}

int main() { long double w, b, ans;

int i, j;

scanf("%Lf%Lf", &w, &b);

for(i=0;i<=w;i++)
    for(j=0;j<=b;j++)
       A[j][i] = -1;

printf("%.12Lf\n", prob(b, w));
return 0;

}