#include <bits/stdc++.h>
#include <boost/multiprecision/cpp_int.hpp>
// #include <atcoder/all>

using boost::multiprecision::cpp_int;
using namespace std;
// using namespace atcoder;

#if __has_include("print.hpp")
  #include "print.hpp"
#endif

#define rep(i, n) for(ll i = 0; i < (ll)(n); i++)
#define per(i, n) for(ll i = n; i >= (ll)(0); i--)
#define ALL(x) (x).begin(), (x).end()
#define RALL(x) (x).rbegin(), (x).rend()
#define MOD 1000000007

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; }

typedef long long ll;
typedef pair<ll, ll> p;

int main(){
  ios::sync_with_stdio(false);
  cin.tie(0);
  int n;
  cin >> n;
  vector<int> a(n);
  rep(i, n) cin >> a[i];
  sort(RALL(a));
  int res = 0;
  vector<int> dish = {a[0]};

  for (int i = 1; i < n; i++) {
    bool ok = false;
    for(auto& elem : dish){
      if(a[i]+1 < elem){
        elem = a[i];
        ok = true;
        break;
      }
    }

    if(!ok) dish.push_back(a[i]);
  }

  res = (int)dish.size();

  cout << res << endl;
}