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