#include <iostream>
#include <fstream>
#include <algorithm>
#include <set>
#include <vector>

#define maxn 5005
using namespace std;

int N;
int v[maxn];
int best[maxn];
int pos[maxn];
int nr_diff = 0;

set <int> aparitii;
vector <int> siruri;
int main()
{
    ifstream in ("secv.in");
    ofstream out ("secv.out");
    int lgmin = 0x7fffffff;
    //cout<<lgmin;
    in>>N;
    for(int i = 1; i <= N; ++i)
    {
        in>>v[i];
        //cout<<v[i]<<" ";
        if(aparitii.find(v[i]) == aparitii.end())
        {
            ++nr_diff;
            aparitii.insert(v[i]);
        }
    }
    //cout<<"\nSALAM\n";
    for(int i = 0; i <= N; ++i)
    {
        best[i] = 1;
        pos[i] = -1;
    }
    for(int i = N - 1; i > 0; --i)
    {
        for(int j = i + 1; j <= N; ++j)
            if(v[i] < v[j] && best[i]<best[j]+1)
            {
            best[i] = best[j] + 1;
            pos[i] = j;
            if(best[i] == nr_diff)
                {
                    siruri.push_back(i);
                    //cout<<i<<"\n";
                }
            }
    }
    if(siruri.empty())
    {
        out<<"-1\n";
        return 0;
    }
    for(int i = 0; i < siruri.size(); ++i)
    {

        int capat = siruri[i];
        while(1)
        {
            //cout<<capat<<"\n";
            if(pos[capat] != -1)
                capat = pos[capat];
            else
                break;
        }
;
        if(capat - siruri[i] < lgmin)
            lgmin = capat - siruri[i];
    }
    out<<lgmin + 1<<"\n";
    return 0;
}