#include <bits/stdc++.h>

using namespace std;
using ll = long long;

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

    ll N, A, ans=0;
    cin >> N;
    set<ll> st;
    map<ll, ll> mp;
    for (int i=0; i<N; i++){
        cin >> A;
        st.insert(A);
        mp[A]++;
    }

    for (auto x : st){
        mp[x+1] += mp[x-1];
    }
    for (auto [x, y] : mp){
        ans += y;
    }
    cout << ans << endl;

    return 0;
}