#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,a,c[100]={0},max=0;
    cin>>n;
    for(int i=0;i<n;i++){
        cin>>a;
        c[a]++;
       }
   for(int i=0;i<99;i++){
       if(max<c[i]+c[i+1]){
           max=c[i]+c[i+1];
       }
   }
    cout<<max;
    return 0;
}