#include <bits/stdc++.h>
using namespace std;
ifstream in("secv.in");
ofstream out("secv.out");
const int N = 5005;
int v[N],dp[N],viz[N];
bool lazynorm[N];
int main()
{
    int n;
    in >> n;
    for (int i = 1; i<=n; i++)
        in >> v[i];
    int k = 0;
    for (int i = 1; i<=n; i++)
    {
        int Min = INT_MAX, poz = 0;
        for (int j = 1; j<=n; j++)
            if (v[j]<Min && !lazynorm[j])
            {
                Min = v[j];
                poz = j;
            }
        if (!poz)
            break;
        k++;
        for (int j = 1; j<=n; j++)
            if (v[j] == Min)
            {
                lazynorm[j] = 1;
                v[j] = k;
            }
    }
    int ans = INT_MAX;
    for (int i = 1; i<=n; i++)
        {
            viz[0] = i;
            for (int j = i; j<=n; j++)
                {
                    if (viz[v[j]-1] == i && viz[v[j]]!=i)
                    {
                        viz[v[j]] = i;
                        dp[v[j]] = j;
                    }
                }
            if (viz[1] == i && viz[k] == i)
                ans = min(ans,dp[k]-dp[1]+1);
        }
    if (ans == INT_MAX)
        out << -1;
    else
        out << ans;
}