#include <algorithm>
#include <climits>
#include <cmath>
#include <iostream>
#include <map>
#include <queue>
#include <set>
#include <stack>
#include <vector>

using namespace std;
using ll = long long;

#define endl '\n'

const ll INF = LLONG_MAX;
const ll MOD = 1e9 + 7;

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    int n;
    cin >> n;
    vector<int> nums(n);
    for (int i = 0; i < n; i++) {
        cin >> nums[i];
    }

    deque<int> dq;
    int l = 0, r = 1;
    int maxx = -1;
    while (r < n) {
        while (!dq.empty() && nums[dq.front()] >= nums[l]) {
            l++;
            while (!dq.empty() && dq.front() <= l) {
                dq.pop_front();
            }
        }
        if (!dq.empty() && nums[r] > nums[dq.front()] && r - l > 1)
            maxx = max(maxx, r - l);

        while (!dq.empty() && nums[dq.back()] <= nums[r]) {
            dq.pop_back();
        }
        dq.push_back(r);
        r++;
    }
    if (maxx > 1)
        cout << maxx;
    else
        cout << -1;
}