#include <bits/stdc++.h>
using namespace std;
 
int main() {
    int n;
    cin >> n;
 
    vector<int> a(n);
    for (int &x : a) cin >> x;
 
    if (n <= 1) {
        cout << n;
        return 0;
    }
 
    int diff = a[1] - a[0];
    int cnt = 2;
    int maxi = 2;
 
    for (int i = 2; i < n; i++) {
        if (a[i] - a[i-1] == diff) {
            cnt++;
        } else {
            diff = a[i] - a[i-1];
            cnt = 2;
        }
 
        maxi = max(maxi, cnt);
    }
 
    cout << maxi << endl;
}

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