#include<cstdio>
#include<iostream>
#include<algorithm>
#include<map>
#include<string>

using namespace std;
int n,a[1000000+100],sol,mapa[10000],maxx;
string s;
int main()
{
    scanf("%d",&n);
    for (int i=1;i<=n;i++)scanf("%d",&a[i]),mapa[a[i]]++;
    for (int i=1;i<=100;i++)maxx=max(mapa[i]+mapa[i+1],maxx);
    cout<<maxx;

    return 0;
}