#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;
    cin >> n;
    vector<int> a(n);
    for (int i=0; i<n;++i){
        cin >>a[i];        
    }
    sort(a.begin(),a.end());
    int max = -1;
    for (int i=0;i<n;++i){
        int count=0;
        for (int j=i;j<n; ++j){
            if (a[j]-a[i] <=1){
                count++;
            } else {
                break;
            }
        }
        if (count>max){
            max = count;
        }
    }
    cout << max << endl;
    return 0;
}