#include <bits/stdc++.h>
#define El 2000000000
#define Dim 5001
using namespace std;
ifstream f("secv.in");
ofstream g("secv.out");
long Sir[Dim],n,maxim,Dist[Dim],L=Dim;

int main()
{
    f>>n;
    for(int i=1;i<=n;i++)
    {
        f>>Sir[i];
        maxim=max(maxim,Sir[i]);
        Dist[i]=5005;
    }
    for(long i=n;i>=1;i--)
     for(long j=i+1;j<=n;j++)
    {
        if(Sir[i]<maxim&&Sir[i]+1==Sir[j])
        {
            if(Dist[j]==5005)
            Dist[j]=j-i;
            else
            Dist[j]=min(Dist[j],j-1);
        }
    }
    for(int i=1;i<=n;i++)
     if(Sir[i]==5) L=min(L,Dist[i]);
    g<<L;

    return 0;
}