#include <iostream>
using namespace std;
int n,c,a,b,d,x;
int main() {
	cin >> n >> b;
	c = 1; 
	for (int i = 1; i < n; i++) {
		cin >> a;
		if (i == 1) {
			x = 2;
		} else if (d == a-b) {
			x++;
		} else {
			c = max(c, x);
			x = 2;
		}
		d = a - b;
		b = a;
	}
	cout << max(x,c) << endl;
}