#include <bits/stdc++.h>
using namespace std;

using ll = long long;

int main() {

    int n;
    cin >> n;

    vector<ll> a(n);
    for (auto &x : a)
        cin >> x;

    if (n <= 1) {
        cout << n << '\n';
        return 0;
    }

    ll diff = a[1] - a[0];
    int len = 2;
    int ans = 2;

    for (int i = 2; i < n; i++) {
        ll currDiff = a[i] - a[i - 1];

        if (currDiff == diff) {
            len++;
        } else {
            diff = currDiff;
            len = 2;
        }

        ans = max(ans, len);
    }

    cout << ans << '\n';

    return 0;
}