#include <algorithm>
#include <iostream>
#include <fstream>
#include <bitset>
using namespace std;
ifstream in("secv.in");
ofstream out("secv.out");
const int maxn = 500005;
pair <int, int> aux[maxn];
bitset <maxn> viz;
int v[maxn];
int mn = (1 << 30);
int nr;
int n;

void incearca(int st)
{
    for(int i = 0; i < maxn; i++)
        viz[i] = 0;
    viz[0] = 1;
    for(int i = st; i <= n; i++)
    {
        if(viz[v[i] - 1])
            viz[v[i]] = 1;
        if(viz[nr] == 1)
        {
            mn = min(mn, i - st + 1);
            return;
        }
    }
    //cerr << st << ":\n";
    //for(int i = 1; i <= n; i++)
        //cerr << viz[i] << " ";
    //cerr << "\n";
    return;
}

int main()
{
    in >> n;
    for(int i = 1; i <= n; i++)
    {
        in >> aux[i].first;
        aux[i].second = i;
    }
    sort(aux + 1, aux + n + 1);
    aux[0].first = -1;
    for(int i = 1; i <= n; i++)
    {
        if(aux[i].first != aux[i - 1].first)
            nr++;
        v[aux[i].second] = nr;
    }
    for(int i = 1; i <= n; i++)
        incearca(i);
    if(mn == (1 << 30))
    {
        out << -1 << "\n";
        return 0;
    }
    out << mn << "\n";
    return 0;
}