Problem:
Score : 400 points

Problem Statement

You are going out for a walk, when you suddenly encounter N monsters. Each monster has a parameter called health, and the health of the i-th monster is h_i at the moment of encounter. A monster will vanish immediately when its health drops to 0 or below.

Fortunately, you are a skilled magician, capable of causing explosions that damage monsters. In one explosion, you can damage monsters as follows:

Select an alive monster, and cause an explosion centered at that monster. The health of the monster at the center of the explosion will decrease by A, and the health of each of the other monsters will decrease by B. Here, A and B are predetermined parameters, and A > B holds.

At least how many explosions do you need to cause in order to vanish all the monsters?

Constraints

All input values are integers.

1 ≤ N ≤ 10^5

1 ≤ B < A ≤ 10^9

1 ≤ h_i ≤ 10^9

Input

Input is given from Standard Input in the following format:

N A B
h_1
h_2
:
h_N

Output

Print the minimum number of explosions that needs to be caused in order to vanish all the monsters.

Sample Input 1

4 5 3
8
7
4
2

Sample Output 1

2

You can vanish all the monsters in two explosion, as follows:

First, cause an explosion centered at the monster with 8 health. The healths of the four monsters become 3, 4, 1 and -1, respectively, and the last monster vanishes.

Second, cause an explosion centered at the monster with 4 health remaining. The healths of the three remaining monsters become 0, -1 and -2, respectively, and all the monsters are now vanished.

Sample Input 2

2 10 4
20
20

Sample Output 2

4

You need to cause two explosions centered at each monster, for a total of four.

Sample Input 3

5 2 1
900000000
900000000
1000000000
1000000000
1000000000

Sample Output 3

800000000

Solution in C++ (Clang 10.0.0) (judge verdict: Accepted)

#include <iostream>
#include <vector>
#include <deque>
#include <algorithm>
#include <numeric>
#include <string>
#include <cstring>
#include <list>
#include <unordered_set>
#include <tuple>
#include <cmath>
#include <limits>
#include <type_traits>
#include <iomanip>
#include <map>
#include <unordered_map>
#include <queue>
#include <stack>
#include <set>
#include <bitset>
#include <complex>
#include <regex>
#include <random>
using namespace std;

#define rep(i,n)	for(lint i = 0; i < n; i++)
#define repr(i,n)	for(lint i = n - 1; i >= 0; i--)
#define repi(i,ini,n)	for(lint i = ini; i < n; i++)
#define repir(i,ini,n)	for(lint i = n-1; i >= ini; i--)
#define repb(i,start,end)	for(lint i = start; i <= end; i++)
#define repbr(i,start,end)	for(lint i = end; i >= start; i--)

#define bit(n)				(1LL << (n))

#define all(v) v.begin(),v.end()
#define rall(v) v.rbegin(),v.rend()
#define rg(v, ini, end) v.begin() + ini, v.begin()+end
#define rrg(v, ini, end) v.rbegin() + ini, v.rbegin()+end

#define ret return 0;

namespace {

	using lint = long long;
	using ulint = unsigned long long;
	using ld = long double;
	struct xy
	{
		lint x, y;
		xy() :x(0), y(0) {}
		xy(lint _x, lint _y) : x(_x), y(_y) {}
		xy operator+(const xy& p) const
		{
			return xy(x + p.x, y + p.y);
		}
		bool operator<(xy p) const
		{
			if (y == p.y)
				return x < p.x;
			return y < p.y;
		}
	};
	struct xyd
	{
		ld x, y;
		xyd() :x(0), y(0) {}
		xyd(long double _x, long double _y) : x(_x), y(_y) {}
	};
	using vec = vector<lint>;
	using vecd = vector<ld>;
	using vecs = vector<string>;
	using vecp = vector<xy>;
	template<class T> using vect = vector<T>;
	class vec2 : public vector<vector<lint>>
	{
	public:
		vec2() {}
		vec2(lint n) : vector(n) {}
		vec2(lint h, lint w) : vector(h, vector<lint>(w)) {}
		vec2(lint h, lint w, lint v) : vector(h, vector<lint>(w, v)) {}
	};

	template<class T> using priq = priority_queue<T>;
	template<class T> using rpriq = priority_queue<T, vector<T>, greater<T>>;
	template<class Key, class Val> using hashmap = unordered_map<Key, Val>;
	template<class Key> using hashset = unordered_set<Key>;

	mt19937 mtrand((random_device())());

	const double pi = 3.141592653589793238462;
	const lint intmax = 9223372036854775807;
	const lint inf = 1100100100100100100LL;

	template<class T>
	constexpr auto msum(T arg0)
	{
		return arg0;
	}

	template<class T, class ...Types>
	constexpr auto msum(T arg0, Types ...args)
	{
		static_assert(sizeof...(args) > 0, "arg err");

		return arg0 + msum(args...);
	}

	template<class It>
	constexpr typename It::value_type mmax(It begin, It end)
	{
		return *max_element(begin, end);
	}

	template<class It>
	constexpr typename It::value_type mmin(It begin, It end)
	{
		return *min_element(begin, end);
	}

	template<class T>
	constexpr auto mmax(T arg)
	{
		return arg;
	}

	template<class T, class ...Types>
	constexpr auto mmax(T arg0, Types ...args)
	{
		using promote_t = decltype(msum(arg0, args...));

		return max(static_cast<promote_t>(arg0), static_cast<promote_t>(mmax(args...)));
	}

	template<class T>
	constexpr auto mmin(T arg)
	{
		return arg;
	}

	template<class T, class ...Types>
	constexpr auto mmin(T arg0, Types ...args)
	{
		using promote_t = decltype(msum(arg0, args...));

		return min(static_cast<promote_t>(arg0), static_cast<promote_t>(mmin(args...)));
	}

	template<class T>
	struct Mplus
	{
		T operator()(const T& a, const T& b)
		{
			return a + b;
		}

		const static T id = T(0);
	};

	template<
		class It,
		class T = typename It::value_type,
		class Monoid = Mplus<T>>
		T acc(It begin, It end, Monoid f = Mplus<T>())
	{
		return accumulate(begin, end, Monoid::id, f);
	}

	constexpr auto clamp(lint val, lint left, lint right)
	{
		return mmax(mmin(val, right), left);
	}

	constexpr lint div2(lint p, lint q)
	{
		return (p + q - 1) / q;
	}

#if(__cplusplus < 201703L)

	lint gcd(lint a, lint b) {
		while (1) {
			if (a < b) swap(a, b);
			if (!b) break;
			a %= b;
		}
		return a;
	}

	lint lcm(lint a, lint b)
	{
		return a / gcd(a, b) * b;
	}

#endif

	constexpr lint powInt(lint a, lint b)
	{
		if (b == 0)
		{
			return 1;
		}
		if (b == 1)
		{
			return a;
		}
		lint tmp = powInt(a, b / 2);
		return (b % 2 == 1 ? a * tmp * tmp : tmp * tmp);
	}

	template<class T>
	T sgn(T val)
	{
		if (val == T(0))
			return T(0);
		if (val < 0)
			return T(-1);
		if (val > 0)
			return T(1);
	}

	template<class T>
	constexpr auto modK_belowN(T k, T MOD, T n)
	{
		return (n + MOD - k - 1) / MOD;
	}

	template<class It, class T>
	bool exist(It begin, It end, const T& val)
	{
		return find(begin, end, val) != end;
	}

	template<class It, class Pr>
	bool exist_if(It begin, It end, Pr pred)
	{
		return find_if(begin, end, pred) != end;
	}

	template<class T>
	bool between(T val, T l, T r)
	{
		return (val >= l) && (val <= r);
	}

	lint extGCD(lint a, lint b, lint& x, lint& y) {
		if (b == 0) {
			x = 1;
			y = 0;
			return a;
		}
		lint d = extGCD(b, a % b, y, x);
		y -= a / b * x;
		return d;
	}

	template<class It>
	auto carr(It begin, It end) {
		vec c;
		c.push_back(1);
		auto before = *begin;
		for (auto it = begin + 1; it != end; it++) {
			if (before != *it) {
				c.push_back(0);
				before = *it;
			}
			c.back()++;
		}
		return c;
	}

	template<class T>
	struct nval {
		lint n;
		T val;
		nval() : n(0) {};
		nval(lint _n, T _val) : n(_n), val(_val) {};
	};

	template<class It>
	auto carr2(It begin, It end) {
		using T = nval<remove_reference_t<decltype(*begin)>>;

		vect<T> c;
		c.push_back(T(1, *begin));
		auto before = *begin;
		for (auto it = begin + 1; it != end; it++) {
			if (before != *it) {
				c.push_back(T(0, *it));
				before = *it;
			}
			c.back().n++;
		}
		return c;
	}

	template<class It, class ...T>
	void sort2(It begin, It end, T ...p)
	{
		using val_t = remove_reference_t<decltype(*begin)>;

		sort(begin, end, [p...](const val_t& a, const val_t& b) {
			bool neq[] = { (a.*p != b.*p)... };
			bool sg[] = { (a.*p < b.*p)... };

			rep(i, sizeof...(p)) {
				if (neq[i])
				{
					return sg[i];
				}
			}
			return false;
		});
	}

	template<class It, class It2>
	auto spacel(It i, It2 end)
	{
		if (i + 1 == end)
		{
			return '\n';
		}
		else
		{
			return ' ';
		}
	}

	bool match(string s, string r)
	{
		return regex_match(s, regex(r));
	}

	ostream& setp(ostream& ost)
	{
		cout << setprecision(60) << fixed;
		return ost;
	}

#ifdef _LOCAL
	auto& dbg = cout;
#else
	struct dummy_cout
	{
		template<class T>
		dummy_cout& operator<<(T&& op)
		{
			return *this;
		}

		using endl_t = basic_ostream<char, char_traits<char>>;

		dummy_cout& operator<<(endl_t& (*)(endl_t&))
		{
			return *this;
		}
	};

	dummy_cout dbg;
#endif

	const ulint mod = 1000000007;
	//const ulint mod = 998244353;
	const ld eps = 0.0000001;
};

template<class T, class Pred>
pair<T, T> bin(T begin, T end, Pred p)
{
	while (end - begin > 1)
	{
		T tgt = begin + (end - begin) / 2;

		if (p(tgt))
		{
			begin = tgt;
		}
		else
		{
			end = tgt;
		}
	}

	return make_pair(begin, end);
}

int main()
{

	lint n, a, b;
	cin >> n >> a >> b;
	vec h(n);
	rep(i, n)
		cin >> h[i];

	sort(rall(h));

	auto ans = bin(0ll, inf, [&](lint c) {

		lint cc = 0;
		rep(i, n)
		{
			lint hh = 0;
			if (div2(h[i], b) > c)
				hh = h[i] - c * b;
			cc += div2(hh, (a - b));
		}

		return cc > c;
		});

	cout << ans.second << endl;
	return 0;
}