#include <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
using namespace std;
int main() 
{
    int n;
    cin>>n;
    int a[10000];
    for(int i = 0; i<n; i++)
        cin>>a[i];
    sort(a, a+n);
    int main = 0;
    for(int j = 0; j<(n - 1); j++)
    {
        int count = 0;
        for(int k = j + 1; k<n; k++)
        {
            if(abs(a[j] - a[k])<=1)
                count++;
        }
        if(count>main)
            main = count;
    }
    cout<<main + 1<<endl;
    return 0;
}