#include <fstream>
#include <algorithm>
using namespace std;

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

const int Nmax = 5005, Inf = 0x3f3f3f3f;

int n, nr, MIN = Inf;
int a[Nmax], b[Nmax], norm[Nmax], last[Nmax], best[Nmax];

int main()
{
    fin >> n;
    if (n == 0)
    {
        fout << -1 << '\n';
        return 0;
    }
    if (n == 1)
    {
        fout << 1 << '\n';
        return 0;
    }
    for (int i = 1; i <= n; ++i)
    {
        fin >> a[i];
        b[i] = a[i];
    }
    sort(b + 1, b + n + 1);
    for ( int i = 1,j = 1; i <= n; ++j)
    {
        b[j] = b[i];
        while (b[j] == b[i])
            ++i;
        nr = j;
    }

    for (int i = 1; i <= n; ++i)
        norm[i] = lower_bound(b + 1, b + nr + 1, a[i]) - b;

    for (int i = 1; i <= n; ++i)
    {
        if (norm[i] == 1)
            best[i] = 1, last[1] = i;
        else if (last[norm[i] - 1])
        {
            best[i] = i - last[norm[i] - 1] + best[last[norm[i] - 1]];
            last[norm[i]] = i;
            if(norm[i] == nr && best[i] < MIN) MIN = best[i];
        }
    }

    if ( MIN == Inf)
        fout << "-1\n";
    else fout << MIN << '\n';
    return 0;
}