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


int main() {
    int n;
    cin >> n;
    int a[n], count[100];
    for(int i = 0; i<100;  i++){
        count[i] = 0;
    }
    for(int i = 0; i<n; i++){
        cin >> a[i];
        count[a[i]]++;
    }
    int res = 0;
    for(int i = 0; i<99; i++){
        if(count[i]+count[i+1]>res){
            res = count[i]+count[i+1];
        }
    }
    cout << res << endl;
    /* Enter your code here. Read input from STDIN. Print output to STDOUT */   
    return 0;
}