#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, x;
    cin >> n;
    
    int arr[100];
    for( int i =0; i < 100; i++ )
        arr[i] = 0;
    
    for( int i =0; i < n; i++ )
    {
        cin >> x;
        arr[x]++;
    }    
    
    int ans = -1;
    for( int i =1; i < 98; i++ )
    {
        ans = max(ans, arr[i] + arr[i+1]);            
    }
    
    cout << ans;
    return 0;
}