#include <fstream>

using namespace std;
ifstream cin("secv.in");
ofstream cout("secv.out");
int n,i,x,v[5005],l,a[5005],b[5005],p,u,mij,mn=99999999,nr,z,poz,ok,j,ind;
int main()
{
    cin>>n;
    for(i=1;i<=n;i++)
    {
        cin>>v[i];
    }
    for(i=1;i<=n;i++)
    {
        x=v[i];
        if(x>a[nr]) {a[++nr]=x;z=i;b[i]=nr;}
        else
        {
            p=1;
            u=nr;
            while(p<=u)
            {
                mij=(p+u)/2;
                if(a[mij]<x) p=mij+1;
                else {poz=mij;u=mij-1;}
            }
            a[poz]=x;
            b[i]=poz;
        }
    }
    for(i=1;i<=n;i++)
    {
        if(b[i]==nr)
        {
            z=nr-1;
            ind=0;
            for(j=i;j>=1;j--)
            {
                if(b[j]==z) {z--;}
                if(z==0) {ind=j;break;}
            }
            if(z==0) mn=min(mn,i-ind+1);
        }
    }
    if(mn==99999999) cout<<-1;
    cout<<mn;
    return 0;
}