#include<bits/stdc++.h>
// #include<atcoder/all>

using namespace std;
// using namespace atcoder;
using ll = long long;
using ull = unsigned long long;
using P = pair<int,int>;
#define rep(i,n) for(ll i = 0;i < (ll)n;i++)
#define ALL(x) (x).begin(),(x).end()
#define MOD 1000000007


int main(){
  
  int n;
  cin >> n;
  vector<int> v(n);
  rep(i,n)cin >> v[i];
  sort(ALL(v));
  rep(i,n-1){
    if(v[i+1]-v[i] == 1){
      cout << 2 << "\n";
      return 0;
    }
  }
  cout << 1 << "\n";
  

  return 0;
}