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


int main() {
    int n;
    cin >> n;
    vector<int> a(100);
    for (int i = 0; i < n; ++i) {
        int x;
        cin >> x;
        ++a[x];
    }
    
    int result = 0;
    for (int i = 1; i < 100; ++i) {
        int s = a[i-1] + a[i];
        if (s > result)
            result = s;
    }
    cout << result << endl;
    return 0;
}