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


int main() {
    int n;
    cin>>n;
    int a[n];
    for(int i=0;i<n;i++){
        cin>>a[i];
    }
    sort(a,a+n);
    int res=0;
    int ans=0;
    for(int i=0;i<n;i++){
        int x=a[i];
        ans=1;
        for(int j=i+1;j<n;j++){
            if(a[j]-x>1)break;
            else ans++;
        }
        if(ans>res)res=ans;
    }
    cout<<res;
    /* Enter your code here. Read input from STDIN. Print output to STDOUT */   
    return 0;
}