#include <cstdio>
#include <iostream>
#include <set>

using namespace std;

int main() {
    freopen("secv.in", "r", stdin);
    freopen("secv.out", "w", stdout);

    ios::sync_with_stdio(false);
    cin.tie(0);

    int dp[5005][5005], v[5005], n;
    set<int> s;
    cin >> n;
    for (int i = 1; i <= n; i++) {
        cin >> v[i];
        s.insert(v[i]);
    }
    set<int>::iterator it = s.begin();
    for (int i = 1; i <= n; i++) {
        if (v[i] == *it) {
            dp[1][i] = 1;
        }
    }
    int ant = *it, k = 2;
    for (it++; it != s.end(); it++) {
        for (int i = 1; i <= n; i++) {
            if (v[i] == *it) {
                for (int j = i - 1; j > 0; j--) {
                    if (v[j] == ant && dp[k - 1][j] > 0) {
                        dp[k][i] = i - j + dp[k - 1][j];
                        break;
                    }
                }
            }
        }
        ant = *it;
        k++;
    }
    k--;
    int ans = 5005;
    for (int i = 1; i <= n; i++) {
        if (dp[k][i] > 0 && dp[k][i] < ans) {
            ans = dp[k][i];
        }
    }
    cout << ((ans == 5005) ? -1 : ans);

    return 0;
}