#include<bits/stdc++.h>
using namespace std;
const int N = 1e2 + 9;
int n,a[N],b[N],ans = 1;
int main()
{
    cin >> n;
    for(int i = 0 ; i < n ; i++)
    {
         cin >> a[i];
         b[a[i]]++;
    }
    for(int i = 1 ; i <= 98 ; i++ )
       ans = max(ans , b[i] + b[i+1]);
    cout << ans;
	return 0;
}