#pragma GCC diagnostic ignored "-Wunused-variable" 
#include <bits/stdc++.h>
using namespace std;

#define BOOST
#ifdef BOOST
#include <boost/multiprecision/cpp_int.hpp>
#include <boost/multiprecision/cpp_dec_float.hpp>
#include <boost/range/adaptor/reversed.hpp>
using namespace boost;
using ml = boost::multiprecision::cpp_int;
using md = boost::multiprecision::cpp_dec_float_100;
#define forir(i, ...) if(ll i=(ll)v.size())for(__VA_ARGS__)if(i--,1)
#define eachr(i, e, c) forir(i, auto &&e: adaptors::reverse(c))
#endif

/***** type *****/
using ll = long long;
using ld = long double;
using pll = pair<long long, long long>;
template <class T> using vt = vector<T>;
template <class T> using vvt = vector<vector<T>>;
template <class T> using vvvt = vector<vector<vector<T>>>;
/***** define *****/
#define all(c) (c).begin(), (c).end()            // begin to end
#define coutd cout << fixed << setprecision(10)  // cout double
#define output(x) do{cout<<x;return 0;}while(0)  // cout return
#define rep(i, b, e) for (ll i = b; i < e; i++)  // repeat
#define repr(i, b, e) for (ll i = b; e < i; i--) // repeat reverse
#define fori(i, ...) if (ll i = -1) for(__VA_ARGS__) if (i++, 1)
#define each(i, e, c) fori (i, auto&& e: c)      // for each
/***** const value *****/
#define llong_max 9223372036854775807            // 9 * 10^18
#define ldbl_max 1.79769e+308                    // 1.7 * 10^308
#define pi 3.1415926535897932                    // 3.14 ...
/***** lambda *****/
auto Ceil = [] // if (a % b != 0) return a / b + 1;
(auto x) { return (ll)ceil(x); };
auto Count = [] // long long count value
(auto b, auto e, auto x) { return (ll)count(b, e, x); };
auto CtoL = [] // char to number
(auto c) { return (ll)c - (ll)'0'; };
auto LtoC = [] // number to char
(auto n) { return (char)('0' + n); };
auto Pow = [] // long long pow
(auto a, auto b) { return (ll)pow(a, b); };
auto Pow2 = [] // long long pow2
(auto n) { return (1LL << n); };
auto Pow10 = [] // long long pow10
(auto n) { return (ll)pow(10, n); };
auto Size = []  // long long collection size
(auto& c) { return (ll)(c).size(); };
auto Sum = [] // long long accumulate
(auto b, auto e) { return accumulate(b, e, 0LL); };

/***** template *****/
template <class T> void MakeVVT
(ll ys, ll xs, vvt<T>& v, T fill = T())
{	// vector<vector<T>> resize + fill
	v.resize(ys); rep(y, 0, ys) v[y].resize(xs, fill);
}
template <class T> void MakeVVVT
(ll zs, ll ys, ll xs, vvvt<T>& v, T fill = T())
{	// vector<vector<vector<T>>> resize + fill
	v.resize(zs); rep(z, 0, zs) MakeVVT(ys, xs, v[z], fill);
}
template <class T> void InputVT
(ll xs, vt<T>& v, T fix = T())
{	// input vector<T> (T != struct) + fix
	v.resize(xs); rep(i, 0, xs) { cin >> v[i]; v[i] += fix; }
}
template <class T> void InputVVT
(ll ys, ll xs, vvt<T>& v, T fix = T())
{	// input vector<vector<T>> (T != struct) + fix
	MakeVVT(ys, xs, v, fix);
	rep(y, 0, ys) rep(x, 0, xs) { cin >> v[y][x]; v[y][x] += fix; }
}
template <class T> void InputVVVT
(ll zs, ll ys, ll xs, vvvt<T>& v, T fix = T())
{	// input vector<vector<vector<T>>> (T != struct) + fix
	v.resize(zs); rep(z, 0, zs) InputVVT(ys, xs, v[z], fix);
}

/**************************************/
/********** BEGIN OF NYA LIB **********/
/**************************************/

namespace NyaGadget {}

namespace NyaGadget
{
	/*** めぐる式二分探索ライブラリ ***/

	struct MeguruSearchResult
	{	// 二分探索の結果を格納する
		long long ok_min = 0;    // okとなる最小値
		long long ok_max = 0;    // okとなる最大値
		long long ok_count = 0;	 // okとなる要素個数
	};

	struct NT_MeguruSeach
	{
		ll N;
		vt<ll> A;
		vt<ll> F;

		bool IsOK(long long mid, long long key)
		{	// 問題毎に新しく定義する
			ll test = 0;
			rep(i, 0, N)
			{	// key = K, mid = ans
				if (0 < A[i] * F[i] - mid) test += A[i] - mid / F[i];
			}
			return test <= key;
		}

		/*
		@brief 二分探索関数
		@param rmin 探索範囲最小値
		@param rmax 探索範囲最大値
		@param key okとなる境界値
		@param res 結果を格納する構造体
		@note
		 rmin < rmax になるように探索範囲を指定すること。
		*/
		void Run(long long rmin, long long rmax, long long key, MeguruSearchResult& res)
		{	// 半開区間 (ng, ok] or [ok, ng) で処理する
			long long ng, ok;
			if (IsOK(rmin, key) && IsOK(rmax, key)) { res = { rmin, rmax, rmax - rmin + 1 }; return; }
			else if (IsOK(rmin, key) && !IsOK(rmax, key)) { ng = rmax + 1; ok = rmin; }
			else if (!IsOK(rmin, key) && IsOK(rmax, key)) { ng = rmin - 1; ok = rmax; }
			else { res = { 0, 0, 0 }; return; }

			while (1 < abs(ok - ng))
			{	// okとngのどちらが大きいかわからないことを考慮して絶対値を取る
				long long mid = (ok + ng) / 2;
				if (IsOK(mid, key)) ok = mid;
				else ng = mid;
			}

			if (ng < ok) res = { ng + 1, ok, abs(ok - ng) };
			else         res = { ok, ng - 1, abs(ok - ng) };
		}
	};
}

/**************************************/
/*********** END OF NYA LIB ***********/
/**************************************/

using namespace NyaGadget;
//using mll = NT_ModLL< 1000000007 >;
//using mll = NT_ModLL< 998244353 >;

int main(void)
{
	ll N, K; cin >> N >> K;
	vt<ll> A; InputVT(N, A);
	vt<ll> F; InputVT(N, F);
	sort(all(A));
	sort(all(F), greater<ll>());

	MeguruSearchResult res;
	NT_MeguruSeach ms;
	ms.A = A; ms.F = F; ms.N = N;
	ms.Run(0, Pow10(12), K, res);

	cout << res.ok_min;
	return 0;
}

Measured memory_bytes: 6528