#include <bits/stdc++.h>
using namespace std;

int main() {
  int n;
  cin >> n;
  vector<int> a(n);
  for (int i = 0; i < n; i++) cin >> a.at(i);
  
  sort(a.begin(), a.end());
  
  bool two = false;
  for (int i = 1; i < n; i++) {
    if (a.at(i) - a.at(i - 1) == 1) two = true;
  }
  
  if (two) cout << 2 << '\n';
  else cout << 1 << '\n';
}