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

int a[110];
int main() {
    /* Enter your code here. Read input from STDIN. Print output to STDOUT */   
    int n ;
    cin >> n;
    int x;
    for(int i = 0; i < n ;i  ++){
        cin >> x;
        a[x]++;
    }
    int ans = 0;
    for(int i = 0 ;i <= 100; i ++){
        ans = max(ans,a[i] + a[i+1]);
    }
    cout << ans << endl;
    
    return 0;
}