#include <bits/stdc++.h>

using namespace std;

using ll = long long;

constexpr char newl = '\n';

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

    int n;
    cin >> n;

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

    ll ans = n;
    for (int i = 1; i < n; i++) {
        if (a[i] - a[i - 1] != 1) continue;
        ll cur = a[i];
        ++ans;
        for (int j = i + 1; j < n; j++) {
            if (a[j] > cur + 2) break;
            if (a[j] < cur + 2) continue;
            cur += 2;
            ++ans;
        }
    }
    cout << ans << newl;

    return 0;
}