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


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