100247F - Battle Fury

using namespace std;
using ll = long long;
using predicate = function<bool(ll)>;
using vll = vector<ll>;
ll n, p, q;
vll a;
ll binary_search(ll lo, ll hi, predicate p)
{
    while (lo < hi)
    {
        ll mid = lo + (hi - lo) / 2;
        if (p(mid) == true)
            hi = mid;
        else
            lo = mid + 1;
    }
    if (p(lo) == false)
        return -1;
    return lo;
}
bool hits_suffice(ll x)
{
    ll total_hits;
    if (p == q)
        total_hits = (*max_element(a.begin(), a.end()) + p - 1) / p;
    else
        total_hits =
            accumulate(a.begin(), a.end(), (ll)0, [x](ll acc, ll ai) -> ll {
                ll ai_prime = ai - x * q;
                ll p_prime = p - q;
                return acc + max((ll)0, (ai_prime + p_prime - 1) / p_prime);
            });
    return x >= total_hits;
}
int main(void)
{
    cin >> n >> p >> q;
    a = vll(n);
    for (auto &x : a)
        cin >> x;
    cout << binary_search(0, 1e9 + 11, hits_suffice) << endl;
    return 0;
}