#include <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
using namespace std;

int arr[205];

int main() 
{
    /* Enter your code here. Read input from STDIN. Print output to STDOUT */   
    int N;
    scanf("%d",&N);
    
    for(int i = 0 ; i<N; i++)
       scanf("%d",&arr[i]);
    sort(arr, arr + N);
    int ans = 0;
    for(int i = 0; i < N; i++)
    {
        int sum = 0;
        int temp = 0;
        for(int j = i + 1; j < N; j++)
        {
            sum += arr[j] - arr[j - 1];
            if(sum <= 1) 
            {
                temp++;
                ans = max(ans, temp);
            }
            else break;
        }
    }
    cout << ans + 1 << endl;
    return 0;
}