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#include<bits/stdc++.h>
using namespace std;
int main(){
int n;
cin>>n;
int a[n];
for(int i=0;i<n;i++)cin>>a[i];
//game starts here
int pd=a[1]-a[0];
int curlen=2;
int maxlen=2;
for(int j=2;j<n;j++)
{
if(pd==a[j]-a[j-1])
{
curlen++;
}else{
pd=a[j]-a[j-1];
curlen=2;
}
maxlen=max(maxlen,curlen);
}
cout<<maxlen<<endl;
}