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


int main() {
    int n;
    cin >> n;
    vector<int> h(101);
    for (int i = 0; i < n; i++) {
        int a;
        cin >> a;
        h[a]++;
    }
    int maxs = 0;
    for (int i = 0; i < 100; i++) {
        maxs = max(maxs, h[i] + h[i + 1]);
    }
    cout << maxs << endl;
    return 0;
}