#include <bits/stdc++.h>
using namespace std;
const int maxn = 3e5 + 30;
int a[maxn];
int t, n;
int main() {
  scanf("%d", &t);
  while (t--) {
    scanf("%d", &n);
    for (int i = 1; i <= n; ++i) scanf("%d", &a[i]);
    a[0] = a[1], a[n + 1] = a[n];
    int max = 0, ans = -1;
    for (int i = 1; i <= n; ++i) {
      if (a[i] > max && (a[i] > a[i - 1] || a[i] > a[i + 1])) {
        ans = i;
        max = a[i];
      }
    }
    printf("%d\n", ans);
  }
  return 0;
}
