#include<bits/stdc++.h>
#define ll long long
#define MOD 1000000007
using namespace std;

int main(){
	ll n;cin>>n;
	ll a[100100];
	ll m[10010]={0};
	for(int i=1;i <=n; i++){
		cin>>a[i];m[a[i]]++;
	}
	//for(int i=1; i<=n; i++)cout<<a[i]<<" ";cout<<endl;
	ll ans = 0;
	for(int i=1; i<=100; i++){
		ans = max(ans, m[a[i]]+m[a[i]+1]);
	}

	cout<<ans<<endl;
	return 0;
}