#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;
int main() {
  int n;
  cin >> n;
  vector<int> a(n);
  for (int i = 0; i < n; i++) {
    cin >> a[i];
  }
  sort(begin(a), end(a));
  int ans = n;
  for (int i = 0; i < n - 1; i++) {
    if (a[i] + 1 < a[i + 1]) {
      ans--;
    }
  }
  cout << ans << '\n';
}