// Created by Armin on 2/17/2025.

#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using pp = pair<int, int>;
using vi = vector<int>;
using vvi = vector<vector<int>>;
using vpi = vector<pair<int, int>>;
using vl = vector<ll>;
using vll = vector<ll>;
using vs = vector<string>;
using vvs = vector<vector<string>>;
using ss = set<string>;
using msi = map<string, int>;
using mint = map<int, int>;
constexpr ll MOD = 1e9 + 7;

int main() {
    ios_base::sync_with_stdio(false); cin.tie(0);
    
    int n; cin >> n;
    vector<int> v(n);
    for (int i = 0; i < n; i++) {
      cin >> v[i];
    }

    int maxleft = 0, maxright = n - 1;
    int res = 0;
    for (int i = 0; i < n; i++) {
      if (v[i] >= v[maxleft]) {
        res = max(res, i - maxleft);
        maxleft = i;
      }
    }

    for (int i = n - 1; i >= 0; i--) {
      if (v[i] >= v[maxright]) {
        res = max(res, maxright - i);
        maxright = i;
      }
    }

    cout << (res >= 2 ? res : -1);
    
    return 0;
}