#include <bits/stdc++.h>
using namespace std;
#define INF 1<<30
#define endl '\n'
#define maxn 100005
#define tc printf("Case %d: ", cs)
#define tcn printf("Case %d:\n", cs);
#define FASTIO ios_base::sync_with_stdio(false), cin.tie(0), cout.tie(0);
typedef long long ll;
const double PI = acos(-1.0);

#define dbg1(x) cerr << #x << " = " << x << endl;
#define dbg2(x, y) cerr << #x << " = " << x << ", " << #y << " = " << y << endl;
#define dbg3(x, y, z) cerr << #x << " = " << x << ", " << #y << " = " << y << ", " << #z << " = " << z << endl;
#define dbg4(w,x, y, z) cerr << #w << " = " << w << ", " <<#x << " = " << x << ", " << #y << " = " << y << ", " << #z << " = " << z << endl;

template < typename F, typename S >
ostream& operator << ( ostream& os, const pair< F, S > & p ) {
	return os << "(" << p.first << ", " << p.second << ")";
}

template < typename T >
ostream &operator << ( ostream & os, const vector< T > &v ) {
	os << "{";
	for (auto it = v.begin(); it != v.end(); ++it) {
		if ( it != v.begin() ) os << ", ";
		os << *it;
	}
	return os << "}";
}

template < typename T >
ostream &operator << ( ostream & os, const set< T > &v ) {
	os << "[";
	for (auto it = v.begin(); it != v.end(); ++it) {
		if ( it != v.begin()) os << ", ";
		os << *it;
	}
	return os << "]";
}

template < typename F, typename S >
ostream &operator << ( ostream & os, const map< F, S > &v ) {
	os << "[";
	for (auto it = v.begin(); it != v.end(); ++it) {
		if ( it != v.begin() ) os << ", ";
		os << it -> first << " = " << it -> second ;
	}
	return os << "]";
}

#define dbg(args...) do {cerr << #args << " : "; faltu(args); } while(0)

clock_t tStart = clock();
#define timeStamp dbg("Execution Time: ", (double)(clock() - tStart)/CLOCKS_PER_SEC)

void faltu () { cerr << endl; }

template <typename T>
void faltu( T a[], int n ) {
	for (int i = 0; i < n; ++i) cerr << a[i] << ' ';
	cerr << endl;
}

template <typename T, typename ... hello>
void faltu( T arg, const hello &... rest) { cerr << arg << ' '; faltu(rest...); }
// Program showing a policy-based data structure.
#include <ext/pb_ds/assoc_container.hpp> // Common file 
#include <ext/pb_ds/tree_policy.hpp>
#include <functional> // for less 
#include <iostream>
using namespace __gnu_pbds;
using namespace std;
// GNU link : https://goo.gl/WVDL6g
typedef tree<int, null_type, less_equal<int>, rb_tree_tag,
        tree_order_statistics_node_update>
        new_data_set;

/**___________________________________________________**/

const int N = 2e5 + 5;
ll n, k;
ll a[N], b[N];
bool can(ll m)
{
	ll res = k;
	//ll mx = 0;
	for (int i = 0; i < n; i++) {
		//if (m == 12) dbg(a[i]*b[i]);
		if (a[i]*b[i] <= m) continue;
		ll tt = a[i] * b[i] - m;
		ll x = (tt + b[i] - 1) / b[i];
		//dbg(a[i], b[i], x);
		ll tm = a[i] - x;
		if (tm < 0)x = a[i];
		//dbg(tm * b[i]);
		if (res - x >= 0)res -= x;
		else return false;
	}
	return true;
}

int main()
{
	FASTIO
	///*
// #ifndef ONLINE_JUDGE
// 	freopen("in.txt", "r", stdin);
// 	freopen("out.txt", "w", stdout);
// 	freopen("error.txt", "w", stderr);
// #endif
//*/

	cin >> n >> k;
	ll sm = 0;
	//priority_queue<ll> PQ;
	for (int i = 0; i < n; i++) {
		cin >> a[i];
		sm += a[i];
		//PQ.push(a[i]);
	}
	for (int i = 0; i < n; i++) cin >> b[i];
	if (sm <= k) {
		cout << 0 << endl;
		return 0;
	}

	// while (k > 0) {
	// 	ll x = PQ.top();
	// 	PQ.pop();
	// 	ll tm = (k + 1ll) / 2ll;
	// 	tm = min(tm, x);
	// 	x -= tm;
	// 	k -= tm;
	// 	PQ.push(x);
	// }
	//dbg(k);
	sort(b, b + n);
	sort(a, a + n);
	reverse(a, a + n);
	ll lo = 0 , hi = 1e18;
	ll ans = 0;
	while (lo < hi) {
		ll m = (lo + hi) / 2;
		//dbg(m);
		if (can(m)) {
			//dbg(m);
			hi = m;
			ans = m;
		}
		else {
			lo = m + 1;
		}
	}
	//dbg(lo);
	cout << ans << endl;
}

Measured memory_bytes: 3328