#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 */
    vector<int>count(101);
    int n, m=0;
    cin>>n;
    while(n--)
    {
        int a;
        cin>>a;
        count[a]+=1;
        if(a>m)
            m=a;
    }
    int max=-1;
    for(int i=1; i<=m; i++)
    {
        int k;
        k=count[i]+count[i+1];
            if(k>max)
                max=k;
    }
    cout<<max;
    return 0;
}