#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++;else s=max(s,c),c=1;
			d=h;
		}s=max(s,c);
		cout<<s;
	}
}