#include <bits/stdc++.h>
using namespace std;long n,a[2010],i,d,s,c,h;int main() {cin>>n;for(i=0;i++<n;){cin>>a[i];}i=0;if(n==1)cout<<1;else{d=a[1]-a[0];c=1;for(;i++<n;){h=a[i+1]-a[i];if(h!=d)c=1;s=max(s,c+++(i!=n));d=h;}cout<<s;}}