#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;
    vector<int> cnt(100, 0);
    cin >> n;
    for (int i = 1; i <= n; ++i)
    {
        int a; cin >> a;    cnt[a] += 1;
    }
    int ans = 0;
    for (int i = 1; i < 100; ++i)
        ans = max(ans, cnt[i]+cnt[i-1]);
    cout << ans << endl;
    return 0;
}