#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;
    vector<int> arr(n),aux(101);
    for(int i=0; i<n ; i++){
        cin >> arr[i];
        aux[arr[i]]++;
    }
    int ans = 0;
    for(int i=1 ; i<100 ; i++){
        if(aux[i]+aux[i+1] > ans){
            ans = aux[i]+aux[i+1];
        }
    }
    cout << ans;
    return 0;
}