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

template <typename T, typename U> bool cmin(T &a, U b) { return a > b && (a = b, true); }
template <typename T, typename U> bool cmax(T &a, U b) { return a < b && (a = b, true); }

signed main() {
  cin.tie(nullptr);
  ios_base::sync_with_stdio(false);

  int N;
  cin >> N;
  vector<int> A(N);
  for (int i = 0; i < N; i++) cin >> A.at(i);
  sort(A.begin(), A.end());
  for (int i = 0; i + 1 < N; i++) {
    if (A.at(i) + 1 < A.at(i + 1)) continue;
    return cout << 2 << "\n", 0;
  }
  cout << 1 << "\n";
}