#include <bits/stdc++.h>
using namespace std;
int main(void) {
  int n;
  scanf("%d", &n);
  int v[n];
  for (int i = 0; i < n; i++) scanf("%d", v + i);
  if (n > 2) {
    for (int i = 0; i + 3 <= n; i++) {
      int a = v[i], b = v[i + 1], c = v[i + 2];
      int ans1 = -1, ans2 = -1;
      set<int> ms;
      ms.insert(a);
      ms.insert(b);
      ms.insert(c);
      if (ms.size() == 1)
        continue;
      else if (ms.size() == 3) {
        if (a == *ms.begin())
          ans1 = i, ans2 = i + 1;
        else if (a == *(++ms.begin()))
          ans1 = i, ans2 = i + 2;
        else if (a == *ms.rbegin())
          ans1 = i, ans2 = i + 1;
      } else if (ms.size() == 2) {
        if (a == c) {
          int d = -1;
          if (i > 0) {
            d = v[i - 1];
            if (d != a)
              ans1 = i - 1, ans2 = i;
            else
              ans1 = i, ans2 = i + 1;
          } else if (i + 3 < n) {
            d = v[i + 3];
            if (d != a)
              ans1 = i + 2, ans2 = i + 3;
            else
              ans1 = i + 1, ans2 = i + 2;
          } else
            continue;
        } else if (a == b)
          ans1 = i + 1, ans2 = i + 2;
        else if (b == c)
          ans1 = i, ans2 = i + 1;
      }
      printf("%d %d\n", ans1 + 1, ans2 + 1);
      return 0;
    }
  }
  printf("-1\n");
  return (0);
}
