#include<iostream>
#include<cstring>
#include<cstdio>
#include<vector>
#include<cmath>
#include<sstream>
#include<algorithm>
#include<set>
#include<queue>
#include<map>
using namespace std;


int main(){
	//freopen("in.txt","r",stdin);
	//freopen("out.txt","w",stdout);
	
	
	int n;	
	while(cin>>n){
		int c[n];
		for(int i=0;i<n;i++)cin>>c[i];
		
		int visited[103];
		memset(visited,0,sizeof(visited));
		for(int i=0;i<n;i++)
			visited[c[i]]++;
		
		int dev=0;
		for(int i=0;i<=101;i++){
			dev=max(dev,visited[i]+visited[i+1]);
		}
		
		cout<<dev<<endl;
	}
	
    return 0;
}