#include<iostream>
#include<bits/stdc++.h>
using namespace std;
int main(){
	int n;
	cin>>n;
	int a[n];
	int i;
	for(i=0;i<n;i++){
		cin>>a[i];
	}
	int hash[101];
	for(i=0;i<=100;i++){
		hash[i] = 0;
	}
	for(i=0;i<n;i++){
		hash[a[i]]++;
	}
	int max = 0;
	for(i=0;i<100;i++){
		if(hash[i]+hash[i+1]>max){
			max = hash[i]+hash[i+1];
		}
	}
	cout<<max;
}