#include<bits/stdc++.h>
using namespace std;int main(){int N,x=1;cin>>N;vector<int>A(N);for(int&a:A)cin>>a;for(int i=0;i<N;i++)for(int j=i+1;j<N;j++)if(A[j]-A[j-1]-A[i+1]+A[i])break;else x=x>j-i+1?x:j-i+1;cout<<x;}