#include <cstring>
#include <iostream>
#include <cstdio>
#include <vector>
#include <algorithm>
#include <map>

using namespace std;

vector<int> countt(105, 0);

int main(){
    //freopen("txt.in", "r", stdin);

    int n, x, lim = 0;
    cin >> n;
    for(int i = 1; i <= n; ++i){
        cin >> x;
        countt[x]++;
        if(x > lim)
            lim = x;
    }

    int maxx = 0;
    for(int i = 0; i <= lim - 1; ++i){
        if(countt[i] + countt[i + 1] > maxx)
            maxx = countt[i] + countt[i + 1];
    }

    cout << maxx << '\n';

    return 0;
}