#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 b[100]={0},a;
    int n;
    cin>>n;
    for(int i=0;i<n;i++)
        {
        cin>>a;
        b[a]=b[a]+1;
    }
    int s=-1,temp;
    for(int i=0;i<n-1;i++)
        {
        temp=b[i]+b[i+1];
        if(temp>s)
            s=temp;
    }
    cout<<s;
    return 0;
}