#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;
    cin >> n;
    int a[100] = {0};
    for (int i = 0; i < n; i++) {
        int k;
        cin >> k;
        a[k]++;
    }
    int largest = 0;
    for (int i = 0; i < 99; i++) {
        largest = max(largest, a[i] + a[i+1]);
    }
    cout << largest << endl;
    return 0;
}