import core.bitop, std.algorithm, std.ascii, std.bigint, std.conv, std.math,
    std.functional, std.numeric, std.range, std.stdio, std.string, std.random,
    std.typecons, std.container, std.format;
static import std.ascii;

// dfmt off
T lread(T = long)(){return readln.chomp.to!T();}
T[] lreads(T = long)(long n){return generate(()=>readln.chomp.to!T()).take(n).array();}
T[] aryread(T = long)(){return readln.split.to!(T[])();}
void scan(TList...)(ref TList Args){auto line = readln.split();
foreach (i, T; TList){T val = line[i].to!(T);Args[i] = val;}}
alias sread = () => readln.chomp();enum MOD = 10 ^^ 9 + 7;
alias PQueue(T, alias less = "a<b") = BinaryHeap!(Array!T, less);
// dfmt on

void main()
{
    long N, K;
    scan(N, K);
    auto A = aryread();
    auto F = aryread();
    A.sort();
    F.sort!"b<a"();
    long ok = 10 ^^ 9 + 1;
    long ng = -1;

    long eval(long x)
    {
        long cost;
        foreach (i; 0 .. N)
        {
            if (x < F[i] * A[i])
                cost += max(0, (F[i] * A[i] - x + F[i] - 1) / F[i]);
        }
        return cost;
    }

    // writeln(ok);
    while (1 < ok - ng)
    {
        long m = (ok + ng) / 2;
        long c = eval(m);
        // writefln("%s %s %s %s", ok, ng, m, c);
        if (c <= K)
        {
            ok = m;
        }
        else
        {
            ng = m;
        }
    }
    writeln(ok);
}
