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


int main()
{
    /* Enter your code here. Read input from STDIN. Print output to STDOUT */   
    int n;
    cin>>n;
    int a[100]={0};
    for(int i=0;i<n;i++)
        {
        int x;
        cin>>x;
        a[x]++;
    }
    int temp=0,ans=0;
    for(int i=1;i<99;i++)
        {
        temp=a[i]+a[i+1];
        if(temp>ans)
            {
            ans=temp;
        }
    }
    cout<<ans<<endl;
    return 0;
}