#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using P = pair<ll, ll>;
#define rep(i, a, b) for(ll i = a; i < b; ++i)
#define rrep(i, a, b) for(ll i = a; i >= b; --i)
constexpr ll inf = 4e18;
struct SetupIO {
    SetupIO() {
        ios::sync_with_stdio(0);
        cin.tie(0);
        cout << fixed << setprecision(30);
    }
} setup_io;
int main(void) {
    ll n;
    cin >> n;
    vector<ll> a(n);
    rep(i, 0, n) {
        cin >> a[i];
    }
    sort(a.begin(), a.end());
    ll ans = n;
    rep(i, 0, n - 1) {
        if(a[i + 1] - a[i] != 1) continue;
        ll left = i + 1, right = n;
        while(right - left > 1) {
            ll mid = (left + right) / 2;
            if(a[mid] - a[i] == mid - i) {
                left = mid;
            } else {
                right = mid;
            }
        }
        ans += (left - i + 1) / 2;
    }
    cout << ans << '\n';
}