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


int main() {
    int n;
    cin >> n;
    vector<int> v(n);
    vector<int> f(110, 0);
    for(int i = 0; i < n; ++i) {
        cin >> v[i];
        f[v[i]]++;
    }
    int ans = 0;
    for(int i = 0; i<  n; i++){
        int right = f[v[i] + 1];
        ans = max(ans, f[v[i]] +  right);
    }
    cout << ans << endl;
   
    return 0;
}