#include <bits/stdc++.h>
#define fr(a, b, c) for(int a = b, __ = c; a < __; ++a)
#define dbg(x) cerr << ">>>> " << x << endl;
#define _ << " , " <<

using namespace std;

int cnt[111];

int main(){
	ios::sync_with_stdio(0);
	int n;
	cin >> n;
	fr(i, 0, n){
		int a;
		cin >> a;
		cnt[a]++;
	}

	int ans = 0;
	fr(i, 0, 100)
		ans = max(ans, cnt[i] + cnt[i+1]);
	
	cout << ans << endl;

	return 0;
}