#include <bits/stdc++.h>
using namespace std;
int a[4], p[4], length[4], q[4], pos[4];
int main() {
  int n, m, top = 0;
  scanf("%d%d", &n, a);
  p[0] = 1;
  for (int i = 2; i <= n; i++) {
    scanf("%d", &m);
    if (m != a[top]) {
      a[++top] = m;
      p[top] = i;
    } else {
      length[top]++;
    }
    if (top > 2) i = n + 1;
  }
  int num = 0;
  q[0] = a[0];
  pos[0] = p[0];
  for (int i = 1; i <= top; i++) {
    bool st = 1;
    for (int j = 0; j < i; j++)
      if (a[j] == a[i]) st = 0;
    if (st) {
      q[++num] = a[i];
      pos[num] = p[i];
    }
  }
  if (num == 0) printf("-1\n");
  if (num == 1) {
    if (top <= 2) {
      int i = 0;
      while ((i <= top) && (length[i] == 0)) i++;
      if (i == 0) {
        printf("%d %d\n", p[1] - 1, p[1]);
      } else {
        if (i > top) {
          printf("-1\n");
        } else {
          printf("%d %d\n", p[i] - 1, p[i]);
        }
      }
    } else {
      printf("%d %d\n", p[0], p[1]);
    }
  }
  if (num >= 2) {
    if (q[0] < q[1]) {
      if (q[1] < q[2])
        printf("%d %d\n", pos[0], pos[1]);
      else
        printf("%d %d\n", pos[0], pos[2]);
    } else {
      if (q[1] > q[2])
        printf("%d %d\n", pos[0], pos[1]);
      else
        printf("%d %d\n", pos[0], pos[2]);
    }
  }
  return 0;
}
