#include <map>
#include <set>
#include <list>
#include <cmath>
#include <ctime>
#include <deque>
#include <queue>
#include <stack>
#include <string>
#include <bitset>
#include <cstdio>
#include <limits>
#include <vector>
#include <climits>
#include <cstring>
#include <cstdlib>
#include <fstream>
#include <numeric>
#include <sstream>
#include <iostream>
#include <algorithm>
#include <unordered_map>

using namespace std;


int main(){
    int n;
    cin >> n;
    int num;
    int count[100] = {0};

    for(int i = 0; i < n; i++){
        cin >> num;
        count[num]++;
    }
    
    int max = 0;
    int sum = 0;
    for (int i=1; i<100; i++) {
        sum = count[i-1] + count[i];
        if (sum > max) max = sum;
    }

    cout << max;
    
    return 0;
}