#include <iostream>
#include <fstream>
#include <algorithm>
#include <vector>
#include <map>
using namespace std;
ifstream f("secv.in");
ofstream g("secv.out");
struct {
    int poz;
}dp[5005][5005];
int n,v[5005],a[5005],k=1,len[5005],mn=5005;
map<int,int> mp;
int main()
{
    f>>n;
    for(int i=1;i<=n;++i)
    {
        f>>v[i];
        a[i]=v[i];
    }
    sort(a+1,a+n+1);
    for(int i=2;i<=n;++i)
    {
        if(a[i]!=a[i-1])
        {
            mp[a[i-1]]=k;
            ++k;
        }
    }
    mp[a[n]]=k;
    for(int i=1;i<=n;++i)
    {
        v[i]=mp[v[i]];
    }
    for(int i=1;i<=n;++i)
    {
        if(v[i]==1)
        {
            len[v[i]]++;
            dp[v[i]][len[v[i]]].poz=i;
        }
        else if(len[v[i]-1])
        {
            len[v[i]]++;
            dp[v[i]][len[v[i]]].poz=dp[v[i]-1][len[v[i]-1]].poz;
        }
        if(v[i]==k) mn=min(mn,i-dp[v[i]][len[v[i]]].poz+1);
    }
    if(mn==5005 && n!=0) g<<"-1";
    else if(n==0) g<<"0";
    else g<<mn;
    return 0;
}