#include <iostream>
#include <vector>
#include <algorithm>
#include <map>

using namespace std;

multimap<int, int> v;

int main()
{
    int n;
    cin >> n;
    int t;
    for (int i = 1; i <= n; ++i)
    {
        cin >> t;
        v.insert({ t, i });
    }
    
    int maxi = 0, res = -1, ind = -1;
    for (auto& e : v)
    {
        if (e.second > maxi)
            maxi = e.second;

        if (maxi - e.second > res)
            res = maxi - e.second;
    }
    if (res == -1)
        cout << -1;
    else
        // TODO: a maxi a legnagyobb koordinata
        //     => a legkissebb a maxi - tavolsag
    
       
    /*
    for (int i = 1; i <= n; ++i)

    
    int maxi = 1, ind=0, t;
    for (int i = 1; i < n; ++i)
    {
        for (int j = i + 1; j <= n; ++j)
        {
            if (v[i] > v[j] && j - i > maxi)
            {
                maxi = j - i;
                ind = i;
            }

        }
    }
    if (ind)
        cout << ind << " " << ind + maxi;
    else
        cout << -1;
        */
}