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

int main() {
  ios::sync_with_stdio(false);

  int N; { cin >> N; }

  vector<int> A(N); {
    for (int i = 0; i < N; ++i) cin >> A[i];
    sort(A.begin(), A.end());
  }

  int res = 0;
  for (int i = 0; i < N; ) {
    ++res;
    int j = i + 1;
    while (j < N && A[j - 1] + 1 < A[j]) ++j;
    i = j;
  }

  cout << min(2, res) << endl;
}