#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;

bool ok(int a, int b){
    if (abs(a-b) <= 1)
        return true;
    return false;
}

int main(){
    int n;
    cin >> n;
    vector<int> a(n);
    int t[101] = {0};
    for(int a_i = 0;a_i < n;a_i++){
       cin >> a[a_i];
        t[a[a_i]]++;
    }
    
    int diff = 2;
    for(int i = 1; i <= 100; i++){
        //if (ok(t[i-1], t[i])){
            if (t[i-1] + t[i] > diff)
                diff = t[i-1] + t[i];
        //}
    }
    cout << diff;
    return 0;
}