using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

using System.Runtime.CompilerServices;
using ll=System.Int64;

public class Contest
{
	static void Swap1<T>(ref T a, ref T b) { T t = a; a = b; b = t; }
	static void Swap2<T>(ref T a, ref T b) where T : IComparable { if (a.CompareTo(b)==1) Swap1(ref a, ref b); }  // b の方が小さければ交換
	static bool Chmin<T>(ref T a, T b) where T : IComparable { if (a.CompareTo(b)== 1) { a = b; return true; } return false; }  // b の方が小さければ a を更新
	static bool Chmax<T>(ref T a, T b) where T : IComparable { if (a.CompareTo(b)==-1) { a = b; return true; } return false; }  // b の方が大きければ a を更新
	static T[][] InitMat<T>(int len1, int len2, T val){ T[][] m = new T[len1][]; for (int i = 0; i < m.Length; i++) m[i] = Enumerable.Repeat(val, len2).ToArray(); return m; }
	static T[][][] InitMat<T>(int len1, int len2, int len3, T val){ T[][][] m = new T[len1][][]; for (int i = 0; i < m.Length; i++) m[i] = InitMat(len2,len3,val); return m; }
	public const long MOD1 = 1000000007; // 10^9+7

	public static void Main() {
		Solve_E();
 	}

	public static void Solve_A() {
		int  n, m;
		MyIO.ReadMulti(out n, out m);



		long ans = n<10&&m<10?n*m:-1;

		MyIO.WriteMulti(ans);

	}
	public static void Solve_B() {
		int  n;
		MyIO.ReadMulti(out n);

		string ans = "No";
		for (int i = 1; i < 10; i++)
		{
			if((n%i==0)&&(n/i<10)) ans="Yes";
		}


		MyIO.WriteMulti(ans);

	}
	public static void Solve_C() {
		ll  n;
		MyIO.ReadMulti(out n);

		ll sq = (long)Math.Sqrt((double)n);
		while(sq*sq<n)sq++;
		ll ans = 0;
		for(ll i=sq;0<i;i--)
		{
			if(n%i==0) {
				ans = n/i+i-2;
				break;
			}
		}


		MyIO.WriteMulti(ans);

	}
	public static void Solve_D() {
		int  a,b,x;
		MyIO.ReadMulti(out a, out b, out x);

		double y = (double)x/(double)a;
		double aa = a;
		double bb = b;

		double ans = 0;
		if(2.0*y>a*b) {
			ans = Math.Atan(2.0*(aa*bb-y)/aa/aa);
		}else{
			ans = Math.PI*0.5 - Math.Atan(2.0*y/bb/bb);
		}



		ans *= 180.0/Math.PI;

		MyIO.WriteMulti(ans);

	}
	public static void Solve_E() {
		ll  n, k;
		MyIO.ReadMulti(out n, out k);
		long[] a, f;
		MyIO.ReadArray(out a);
		MyIO.ReadArray(out f);

		Array.Sort(a);
		Array.Sort(f,(x,y)=>(int)(y-x));

		ll max=0;
		for (int i = 0; i < n; i++)
		{
			Chmax(ref max,(long)a[i]*(long)f[i]);
		}
 
		Func<long,bool> ff = (l)=>{
			long kk = k;
			for (int i = 0; i<n; i++)
			{
				if(l<a[i]*f[i]) {
					ll r = l/f[i];
					kk-=a[i]-r;
					if(kk<0) return false;
				}
			}
 
			return true;
		};
 
		long right = max;
		long left = -1;
        while (right - left > 1) {
            long mid = left + (right - left) / 2;
 
            if (ff(mid)) right = mid;
            else left = mid;
        }
 
 
 
		MyIO.WriteMulti(right);

	}
	public static void Solve_F() {
		int  n, m;
		MyIO.ReadMulti(out n, out m);



		long ans = 0;

		MyIO.WriteMulti(ans);

	}




    public static long[] PrimeFactor(long n) {
		List<long> ret = new List<long>();
        if (n < 2) return ret.ToArray();
        while ((n & 1) == 0) {
			ret.Add(2);
			n >>= 1;
		}
        while ((n % 3) == 0) {
			ret.Add(3);
			n /= 3;
		}
        long sqrt = (long)Math.Sqrt(n);
        for (long i = 5, f = 2; i <= sqrt; i += f, f ^= 6) {
            while ((n % i) == 0) {
				ret.Add(i);
				n /= i;
			}
        }
		if(1<n) ret.Add(n);
        return ret.ToArray();
    }












}


















#region MyIO

public struct VT<T, U>
{
	public T Item1; public U Item2;
    public VT(T a, U b) { Item1 = a; Item2 = b; }
}
public struct VT<T, U, V>
{
	public T Item1; public U Item2; public V Item3;
    public VT(T a, U b, V c) { Item1 = a; Item2 = b; Item3 = c; }
}
public struct VT<T, U, V, W>
{
	public T Item1; public U Item2; public V Item3; public W Item4;
    public VT(T a, U b, V c, W d) { Item1 = a; Item2 = b; Item3 = c; Item4 = d; }
}

public class Printer : System.IO.StreamWriter
{
	public override IFormatProvider FormatProvider { get { return System.Globalization.CultureInfo.InvariantCulture; } }
	public Printer(System.IO.Stream stream) : base(stream, new UTF8Encoding(false, true)) { }
	public Printer(System.IO.Stream stream, Encoding encoding) : base(stream, encoding) { }
}
public static class MyIO
{
	private static char[] splitter = new char[] {' '};
	private static bool eq<T, U>() => typeof(T).Equals(typeof(U));
	private static T ct<T, U>(U a) => (T)Convert.ChangeType(a, typeof(T));
	private static T cv<T>(string s) =>
		eq<T, int>()    ? ct<T, int>(int.Parse(s))
	  : eq<T, long>()   ? ct<T, long>(long.Parse(s))
	  : eq<T, double>() ? ct<T, double>(double.Parse(s, System.Globalization.CultureInfo.InvariantCulture))
	  : eq<T, char>()   ? ct<T, char>(s[0])
						: ct<T, string>(s);
			
	public static string[] ReadMulti<T>(out T a) {
		var ar = Console.ReadLine().Split(splitter, StringSplitOptions.RemoveEmptyEntries); 
		a = cv<T>(ar[0]);
		return ar;
	}
	public static string[] ReadMulti<T, U>(out T a, out U b) {
		var ar = ReadMulti<T>(out a); 
        b = cv<U>(ar[1]);
		return ar;
	}
	public static string[] ReadMulti<T, U, V>(out T a, out U b, out V c) {
		var ar = ReadMulti<T, U>(out a, out b); 
        c = cv<V>(ar[2]);
		return ar;
	}
	public static string[] ReadMulti<T, U, V, W>(out T a, out U b, out V c, out W d) {
		var ar = ReadMulti<T, U, V>(out a, out b, out c); 
        d = cv<W>(ar[3]);
		return ar;
	}
	public static string[] ReadMulti<T, U, V, W, X>(out T a, out U b, out V c, out W d, out X e) {
		var ar = ReadMulti<T, U, V, W>(out a, out b, out c, out d); 
        e = cv<X>(ar[4]);
		return ar;
	}
	public static string[] ReadMulti<T, U, V, W, X, Y>(out T a, out U b, out V c, out W d, out X e, out Y f) {
		var ar = ReadMulti<T, U, V, W, X>(out a, out b, out c, out d, out e); 
        f = cv<Y>(ar[5]);
		return ar;
	}
	public static string[] ReadArray<T>(out T[] a) {		
		var ar = Console.ReadLine().Split(splitter, StringSplitOptions.RemoveEmptyEntries);
		a = ar.Select(cv<T>).ToArray();
		return ar;
	}		
	public static string[][] ReadLines<T>(long n, out T[] a) {
		a = new T[n];
		string[][] arr = new string[n][];
		for(int i=0; i<n; i++) arr[i] = ReadMulti(out a[i]);
		return arr;
	}
	public static string[][] ReadLines<T, U>(long n, out VT<T, U>[] a) {
		a = new VT<T, U>[n];
		string[][] arr = new string[n][];
		for(int i=0; i<n; i++) {
			T o; U p;
			arr[i] = ReadMulti(out o, out p);
			a[i] = new VT<T, U>(o, p);
		}
		return arr;
	}
	public static string[][] ReadLines<T, U, V>(long n, out VT<T, U, V>[] a) {
		a = new VT<T, U, V>[n];
		string[][] arr = new string[n][];
		for(int i=0; i<n; i++) {
			T o; U p; V q;
			arr[i] = ReadMulti(out o, out p, out q);
			a[i] = new VT<T, U, V>(o, p, q);
		}
		return arr;
	}
	public static string[][] ReadLines<T, U, V, W>(long n, out VT<T, U, V, W>[] a) {
		a = new VT<T, U, V, W>[n];
		string[][] arr = new string[n][];
		for(int i=0; i<n; i++) {
			T o; U p; V q; W r;
			arr[i] = ReadMulti(out o, out p, out q, out r);
			a[i] = new VT<T, U, V, W>(o, p, q, r);
		}
		return arr;
	}
	public static string[][] ReadMatrix<T>(long n, out T[][] a) {
		a = new T[n][];
		string[][] arr = new string[n][];
		for(int i=0; i<n; i++) arr[i] = ReadArray(out a[i]);
		return arr;
	}

	private static void wwp(Action act){
		var sw = new Printer(Console.OpenStandardOutput()){AutoFlush = false};
		Console.SetOut(sw);
		act();
		Console.Out.Flush();
		sw.AutoFlush = true;
		Console.SetOut(sw);
	}
	private static string wfm(Type t) =>t.Equals(typeof(double)) ? "{0:F10}" : "{0}";
	public static void WriteMulti(params object[] a) {
		wwp(()=>{
			for(int i=0;i<a.Length;i++) {
				string fs = wfm(a[i].GetType()) + ((i<a.Length-1) ? " " : Environment.NewLine);
				Console.Write(fs, a[i]);
			}
		});
	}
	public static void WriteArray<T>(T[] a) {
		wwp(()=>{
			string fs = wfm(typeof(T));
			string fs1 = fs + " ";
			string fs2 = fs + Environment.NewLine;
			for(int i=0;i<a.Length;i++) Console.Write( ((i<a.Length-1) ? fs1 : fs2), a[i]);
		});
	}
	public static void WriteLines<T>(T[] a) {
		wwp(()=>{
			string fs = wfm(typeof(T)) + Environment.NewLine;
			foreach(T x in a) Console.Write(fs, x);
		});
	}


}

#endregion



Measured memory_bytes: 39540