#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,max=-1;
    cin>>n;
    int arr[n];
    for(int i=0;i<n;i++)
        cin>>arr[i];
    int hash[101]={0};
    for(int i=0;i<n;i++)
        hash[arr[i]]++;
    for(int i=1;i<100;i++)
    {
        if(hash[i]+hash[i-1] >max)
            max=hash[i]+hash[i-1];
    }
    cout<<max<<endl;
    return 0;
}