using System;
using System.Collections.Generic;
using System.Windows;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Atcoder
{
    public class Program
    {
        private static long mod = 1000000007;

        static void Main(string[] args)
        {
            var r1 = ReadSplit();
            var n = r1[0].Int();
            var k = r1[1].Long();
            var al = new long[n];
            var fl = new long[n];
            var r2 = ReadSplit();
            var r3 = ReadSplit();
            for (int i = 0; i < n; i++)
            {
                al[i] = r2[i].Long();
                fl[i] = r3[i].Long();
            }
            Array.Sort(al);
            al = al.Reverse().ToArray();
            Array.Sort(fl);

            var max = 0L;
            for (int i = 0; i < n; i++)
            {
                max = Math.Max(max, al[i] * fl[i]);
            }
            long left = 0L;
            long right = max;
            long ans = max;
            if (al.Sum() <= k)
            {
                WriteRead(0);
                return;
            }
            while (right - left > 1)
            {
                long sum = 0L;
                long x = (right + left) / 2;
                for (int i = 0; i < n; i++)
                {
                    sum += Math.Max(0L, al[i] - (x / fl[i]));
                }
                if (k >= sum)
                {
                    ans = Math.Min(ans, x);
                    right = x;
                }
                else
                {
                    left = x;
                }
            }
            WriteRead(ans);
        }

        public static string Read()
        {
            return Console.ReadLine();
        }

        public static string[] ReadSplit()
        {
            return Console.ReadLine().Split(' ');
        }

        public static void WriteRead(object str)
        {
            Console.WriteLine(str);
            Read();
        }

        public static void Write(object str)
        {
            Console.WriteLine(str);
        }

        private static bool ChangeMin<T>(ref T a, T b) where T : IComparable
        {
            if (a.CompareTo(b) > 0)
            {
                a = b;
                return true;
            }
            return false;
        }

        private static bool ChangekMax<T>(ref T a, T b) where T : IComparable
        {
            if (b.CompareTo(a) > 0)
            {
                a = b;
                return true;
            }
            return false;
        }
    }
}


public static class Extentions
{
    public static int Int(this object obj)
    {
        return int.Parse(obj.ToString());
    }

    public static long Long(this object obj)
    {
        return long.Parse(obj.ToString());
    }

    public static decimal Decimal(this object obj)
    {
        return decimal.Parse(obj.ToString());
    }

    public static double Double(this object obj)
    {
        return double.Parse(obj.ToString());
    }

    public static T2 GetValueZero<T1, T2>(this Dictionary<T1, T2> d, T1 key) where T2 : struct
    {
        T2 value;
        if (d.TryGetValue(key, out value))
        {
            return value;
        }
        return new T2();
    }
}



Measured memory_bytes: 51744