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

int arr[100];

int main() {
    /* Enter your code here. Read input from STDIN. Print output to STDOUT */   
    int n, temp;
    cin >> n;
    for (int i = 0; i < n; i++) {
        cin >> temp;
        arr[temp]++;
    }
    int max = 0;
    for (int i = 1; i < 100; i++) {
        if (arr[i] + arr[i - 1] > max)
            max = arr[i] + arr[i - 1];
    }
    cout << max << endl;
    return 0;
}