#include <stdio.h>
#include <bits/stdc++.h>
using namespace std;
#define rep(i,n) for (int i = 0; i < (n); ++i)
#define Inf 1000000005


int main(){

	int N;
	cin>>N;
	
	vector<int> A(N);
	rep(i,N)cin>>A[i];
	
	sort(A.begin(),A.end());
	
	rep(i,N-1){
		if(A[i]+1>=A[i+1]){
			cout<<2<<endl;
			return 0;
		}
	}
	
	cout<<1<<endl;

	return 0;
}