#include <bits/stdc++.h>
using namespace std;
#define overload3(_NULL, _1, _2, name, ...) name
#define rep1(i, n) for (remove_const_t<remove_reference_t<decltype (n)>> i = 0; i < (n); i++)
#define rep2(i, a, b) for (remove_const_t<remove_reference_t<decltype (a)>> i = a; i < (b); i++)
#define rep(...) overload3 (__VA_ARGS__, rep2, rep1) (__VA_ARGS__)
#if __has_include(<debug.hpp>)
#    include <debug.hpp>
#else
#    define dbg(...) (void (0))
#endif
template<class T> void drop (const T &x) {
    cout << x << "\n";
    exit (0);
}
template<class T> bool chmax (T &a, const T &b) { return a < b and (a = b, true); }
template<class T> bool chmin (T &a, const T &b) { return a > b and (a = b, true); }
using i64 = long long;
using usize = size_t;

int main() {
    usize n;
    cin >> n;
    set<int> s{ istream_iterator<int>{ cin }, istream_iterator<int>{} };
    int ans = 0;
    rep (i, 3, 36) if (s.count (i) > 0 and s.count (i - 1) == 0) ans += i;
    cout << ans << "\n";
}

struct IOSetup {
    IOSetup() noexcept {
        ios::sync_with_stdio (false);
        cin.tie (nullptr);
        cout << fixed << setprecision (10);
        cerr << fixed << setprecision (10);
    }
} iosetup;