#include <cstdio>
#include <vector>
#include <set>
#include <algorithm>
using namespace std;

vector<int> v, t;

int main()
{
    freopen("secv.in", "r", stdin);
    freopen("secv.out", "w", stdout);

    int n, i, j, k, x, ans;
    scanf("%d", &n);
    for(i = 1; i <= n; ++i)
    {
        scanf("%d", &x);
        v.push_back(x);
        t.push_back(x);
    }
    sort(t.begin(), t.end());
    t.push_back(2000000001);
    ans = n+1;
    for(i = 0; i < n; ++i)
    {
        k = 0;
        for(j = i; j < n && k < n; ++j)
        {
            while(v[j] == t[k])
                ++k;
        }
        if(k == n)
        {
            if(j-i < ans)
                ans = j-i;
        }
    }
    if(ans == n+1)
        printf("-1");
    else
        printf("%d", ans);
    return 0;
}