#include <iostream>
#include <cassert>
#include <cstdio>
#include <math.h>
#include <algorithm>
#include <time.h>
#define ll long long
#define MAXN 100000
#define MODD 1000000007
using namespace std;

int counts[111];

int main() {
    int n;
    cin>>n;
    
    
    for(int i=0;i<=101;i++)
        counts[i]=0;
    for(int i=0;i<n;i++) {
        int x;
        cin>>x;
        counts[x]++;
    }
    
    int answer = 0;
    for(int i=1;i<=101;i++) {
        answer = max(answer, counts[i]+counts[i-1]);
    }
    
    
    cout << answer << endl;
    
}