#include <cstdio>
#include <cstring>
#include <cmath>
#include <vector>
#include <cstdlib>
#include <iostream>
#include <queue>
#include <set>
#include <map>
#include <algorithm>
#include <stack>
#define MOD 1000000007
#define endl '\n'
#define REP(i,n) for(int i=0;i<n;i++)

using namespace std;

int arr[102];
int main()
{
    int c;
    cin>>c;
    REP(i,c)
    {
        int x;
        cin>>x;
        arr[x]++;
    }
    int maxsize=0;
    REP(i,c-1)
    {
        maxsize=max(maxsize,arr[i]+arr[i+1]);
    }
    cout<<maxsize<<'\n';
    return 0;
}