80分，不知道哪里出问题了

int main()
{
    int i, j, k, n, a[110], ans = 0;
    int sum[30000] = { 0 };
    scanf("%d", &n);
    for (i = 1;i <= n;i++) {
        scanf("%d", &a[i]);
    }
    sort(a + 1, a + n);
    for (i = 3;i <= n;i++)
        for (j = 1;j <= i - 2;j++)
            for (k = j + 1;k <= i - 1;k++) {
                if (a[i] == a[j] + a[k]) {
                    sum[a[i]] = 1;
                }
            }
    for (i = 1;i <= n;i++) {
        if (sum[a[i]] == 1) ans++;
    }
    cout << ans;
    return 0;
}