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

int ar[101];
int main() {
    /* Enter your code here. Read input from STDIN. Print output to STDOUT */   
    int n;
    cin >> n;
    int a;
    
    for(int i = 0 ; i < n ; i++){
        
        cin >> a;
        ar[a]++;
        
    }
    int ans = 0;
    for(int i = 0 ; i < 100; i++)
    {
        
        ans = max(ans,ar[i] + ar[i + 1]);
        
    }    
    cout << ans << "\n";
    return 0;
}