hdu 5207 BestCoder Round #38 ($) Greatest Greatest Common Divisor

#include<stdio.h>
#include<string.h>
#include<math.h>
int flag[];
int a[];
int main()
{
    int sb;
    scanf("%d", &sb);
    int u;
    for (u = ; u <= sb; u++)
    {
        int n, i;
        int maxn = -;
        scanf("%d", &n);
        memset(flag, , sizeof(flag));
        for (i = ; i <= n; i++)
        {
            scanf("%d", &a[i]);
            if (a[i] >= maxn) maxn = a[i];
        }
        for (i = ; i <= n; i++)
        {
            int j;
            for (j = ; j *j <= a[i]; j++)
            {
                if (a[i] % j ==  && j*j < a[i]) flag[j]++, flag[a[i] / j]++;
                else if (a[i] % j ==  && j*j == a[i]) flag[j]++;
            }
        }
        int ans;
        for (i = maxn; i >= ; i--)
        {
            if (flag[i] >= ) { ans = i; break; }
        }
        printf("Case #%d: ", u);
        printf("%d\n", ans);
    }
    return ;
}