#include <bits/stdc++.h>
using namespace std;
#include <math.h>
#include <iomanip>
#include <cstdint>
#include <string>
#include <sstream>
template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; }
#define rep(i,n) for (int i = 0; i < (n); ++i)
typedef long long ll;
using P = pair<int,int>;
const int INF=1001001001;
const int mod =1e9+7;

int main() {
  int N;cin>>N;
  vector<int>A(N);
  rep(i,N){cin>>A[i];}
  sort(A.begin(),A.end());
  bool ok=true;
  for(int i=0;i<N-1;i++){
    if(abs(A[i+1]-A[i])<=1){ok=false;}
  }
  if(ok){cout<<1<<endl;}
  else{cout<<2<<endl;}
  return 0;
}