#include <fstream>
#include <vector>
#include <algorithm>
#define INF 10000
using namespace std;

ifstream fin("secv.in");
ofstream fout("secv.out");

int a[6000], f[6000];
vector <int> s;
int n, i, lmin(INF), l, k;

int main()
{
    fin >> n;
    for (i = 0; i < n; ++i)
    {    
        fin >> a[i];
        f[i] = a[i];
    }    
    
    fin.close();
    sort(f, f + n);
    for (i = 0; i < n; ++i)
    {
        while (i < n && f[i] == f[i+1]) i++;
        s.push_back(f[i]);
       
    }
 // for ( i = 0; i < s.size(); ++i) fout << s[i] << ' ';
    for (i = 0; i < n; i++)
        if (a[i] == s[0])
        {
            l = i;
            k = 1;
            while (l < n && k < s.size())
            {
                if (a[l] == s[k]) k++;
                l++;
            }
            if (k == s.size())
            {
                if (l == i && lmin == INF) lmin = 1;
                else
                if (l-i < lmin) lmin = l-i;
                
            }
        }
    if ( lmin != INF) fout << lmin << '\n';
    else fout << -1 << '\n';
    fout.close();
    return 0;
}