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


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