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