#include <bits/stdc++.h>
using namespace std;
bool cmp(int a, int b) { return (a > b); }
int main() {
  vector<int> arr;
  vector<int> a;
  vector<int> b;
  int n, i, f = 0;
  cin >> n;
  for (i = 0; i < n; i++) {
    int x;
    cin >> x;
    arr.push_back(x);
    a.push_back(x);
    b.push_back(x);
  }
  sort(a.begin(), a.end(), cmp);
  sort(b.begin(), b.end());
  for (i = 1; i < n; i++)
    if (arr[i] != arr[i - 1] &&
        (!((arr[i] == a[i - 1] && arr[i - 1] == a[i]) ||
           (arr[i] == b[i - 1] && arr[i - 1] == b[i])))) {
      cout << i << " " << i + 1 << endl;
      return 0;
    }
  cout << "-1" << endl;
  return 0;
}
