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


int main() {
    /* Enter your code here. Read input from STDIN. Print output to STDOUT */   
    int n;
    cin>>n;
    int a[n+1],hash[105];
    for(int i=0;i<=100;i++) hash[i]=0;
    for(int i=0;i<n;i++){
        cin>>a[i];
        hash[a[i]]++;
    }
  
    int count=0;
    for(int i=0;i<100;i++){
     //   cout<<hash[i]<<" "<<hash[i+1]<<endl;
        if((hash[i]+hash[i+1] )> count) count=(hash[i]+hash[i+1] );
        
    }
    cout<<count;
    return 0;
}