// dfmt off
T lread(T=long)(){return readln.chomp.to!T;}T[] lreads(T=long)(long n){return iota(n).map!((_)=>lread!T).array;}
T[] aryread(T=long)(){return readln.split.to!(T[]);}void arywrite(T)(T a){a.map!text.join(' ').writeln;}
void scan(L...)(ref L A){auto l=readln.split;foreach(i,T;L){A[i]=l[i].to!T;}}alias sread=()=>readln.chomp();
void dprint(L...)(lazy L A){debug{auto l=new string[](L.length);static foreach(i,a;A)l[i]=a.text;arywrite(l);}}
static immutable MOD=10^^9+7;alias PQueue(T,alias l="b<a")=BinaryHeap!(Array!T,l);import std, core.bitop;
// dfmt on

void main()
{
    long N, K;
    scan(N, K);
    auto A = aryread();
    auto F = aryread();
    A.sort();
    F.sort!"b<a";
    long eval(long x)
    {
        long ret;
        foreach (i; 0 .. N)
        {
            ret += A[i] - (x / F[i]);
        }
        return ret;
    }

    long ok = 2_000_000_000_000;
    long ng = -1;
    while ((ok - ng) > 1)
    {
        long m = (ok + ng) / 2;
        if (eval(m) <= K)
        {
            ok = m;
        }
        else
        {
            ng = m;
        }
    }
    writeln(ok);
}
