#include <bits/stdc++.h>
//#include <iostream>
#include <atcoder/all>
#include <math.h>
#define rep(i, n) for(int i = 0; i < (n); i++)
#define rrep(i, n) for(int i = (n-1); i >= 0; i--)
using namespace std;
using namespace atcoder;
typedef long long ll;
const int MOD = 1000000007;
//const int MOD =  998244353;
 
const ll INF = 1LL<<61;
const int IINF = 1000000000;
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 pair<int, int> PI;
typedef pair<ll, ll> P;
typedef pair<string, ll> PS;

using mint = modint1000000007;

int main(){

    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    int N; cin >> N;
    vector<ll> A(N);
    rep(i,N) cin >> A[i];

    sort(A.rbegin(), A.rend());

    priority_queue<ll> que;
    que.push(A[0]);
    ll ans = 1;
    for(int i = 1; i < N; i++){
        ll maxv = que.top(); que.pop();
        if(maxv > A[i]+1){
            que.push(A[i]);
        }
        else{
            ans++;
            que.push(maxv);
            que.push(A[i]);
        }
    }
    cout << ans << endl;
}