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

#define ll long long
const int N = 2e5 + 5, MOD = 1e9 + 7;

int freq[105];

int main(){
	int n, tmp;
	cin>>n;
	for(int i = 1; i <= n; i++){
		cin>>tmp;
		freq[tmp]++;
	}
	int ans = 0;
	for(int i = 1; i <= 100; i++){
		ans = max(ans, freq[i] + freq[i + 1]);
	}
	cout<<ans<<endl;
}