#include <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
using namespace std;


int main(){
    int n,ar[109]={},a,i,tans,ans;
    cin>>n;
    ans=-1;
    while(n--){
        cin>>a;
        ar[a]++;
    }
    for(i=0;i<105;i++){
        tans=ar[i]+ar[i+1];
        if(tans>ans)    ans=tans;
    }
    cout<<ans;
    return 0;
}