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