#include<iostream>
#include<algorithm>
using namespace std;
int N;
int A[1<<17];
main()
{
	cin>>N;
	for(int i=0;i<N;i++)cin>>A[i];
	sort(A,A+N);
	for(int i=1;i<N;i++)if(A[i-1]+1==A[i])
	{
		cout<<2<<endl;
		return 0;
	}
	cout<<1<<endl;
}