#include <iostream>
#include <vector>

int main()
{
    //std::cout << "Hello World!\n";
    int n;
    std::cin >> n;
    std::vector<std::pair<int, bool>> a(n, std::pair<int, bool>(0, true));
    std::vector<int> result;

    int sum = 0;

    for (int i = 0; i < n; ++i) {
        std::cin >> a[i].first;
        sum += a[i].first;
    }

    if ((sum * 2) % n != 0) {
        std::cout << "-1" << std::endl;
        return 0;
    }

    int generalSum = (sum * 2) / n;

    for (int i = 0; i < n; ++i) {
        int firstNum = a[i].first;
        for (int j = 0; j < n; ++j) {
            int isDone = false;
            if (a[j].second && (firstNum + a[j].first) == generalSum) {
                //result[i] = a[j].first;
                a[j].second = false;
                result.push_back(j + 1);
                //std::cout << j + 1 << ' ';
                isDone = true;
            }

            if (!isDone) {
                std::cout << "-1" << std::endl;
                return 0;
            }
        }
    }

    //for (int i = 0; i)


}