#include <bits/stdc++.h>
using namespace std;

int main() {
	int n;
	cin >> n;
	vector<int> v(n), ind(n+1);
	for(int i = 0; i < n; i++) {
		cin >> v[i];
		ind[v[i]] = i+1;
	}

	int ln = v[0], lk = v[n-1], l = 0, r = n-1;
	bool valt = true;
	while(l <= r) {
		if(ln > lk) {
			cout << ind[ln] << ' ' << ind[lk];
			break;
		}
		if(v[l+1] > lk) {
			l++;
			ln = max(ln, v[l]);
		} else if(v[r-1] < ln) {
			r--;
			lk = min(lk, v[r]);
		} else if(v[l+1] > ln) {
			l++;
			ln = max(ln, v[l]);
		} else if(v[r-1] < lk) {
			r--;
			lk = min(lk, v[r]);
		} else if(v[l+1] > v[l]) {
			l++;
			ln = max(ln, v[l]);
		} else if(v[r-1] < v[r]) {
			r--;
			lk = min(lk, v[r]);
		} else if(valt) {
			l++;
			ln = max(ln, v[l]);
		} else {
			r--;
			lk = min(lk, v[r]);
		}
		valt = !valt;
	}
	if(l > r) cout << -1;

	return 0;
}