1
3
5 3 4
 6
5
5 3 4 4 5
3
1 1 1
5
4 4 3 4 4
5
5 5 4 3 2
3
1 1 2
5
5 4 3 5 5
 1
3
10 1 5

1
 1
-1
2
2
3
1
 1

#include <bits/stdc++.h>
using namespace std;
int main() {
  int t, n, k;
  vector<long long int> v;
  cin >> t;
  while (t--) {
    cin >> n;
    for (int i = 0; i < n; i++) {
      v.push_back(0);
      cin >> v[i];
    }
    long long int chk = 0, ans = -1, cnt = 0;
    for (int i = 0; i < n; i++) {
      if (v[i] > cnt) cnt = v[i];
    }
    for (int i = 0; i < n; i++) {
      if (i == 0) {
        if (v[i] == cnt && v[i] > v[i + 1]) ans = i + 1;
      } else if (i == n - 1) {
        if (v[i] == cnt && v[i] > v[i - 1]) ans = i + 1;
      } else if (v[i] == cnt && (v[i] > v[i + 1] || v[i] > v[i - 1]))
        ans = i + 1;
    }
    cout << ans << endl;
  }
  return 0;
}
