import std.stdio, std.conv, std.string, std.array, std.range, std.algorithm, std.container;
import std.math, std.random, std.bigint, std.datetime, std.format;
void main(string[] args){ if(args.length > 1) if(args[1] == "-debug") DEBUG = 1; solve(); }
void log()(){ writeln(""); } void log(T, A ...)(T t, lazy A a){ if(DEBUG) write(t, " "), log(a); } bool DEBUG = 0; 
string rstring(){ static string[] ss; while(!ss.length) ss = readln.chomp.split; string res = ss[0]; ss.popFront; return res; }
T rtype(T)(){ return rstring.to!T; } alias rint = rtype!int, rlong = rtype!long, rreal = rtype!real;
T[] rtypes(T)(int n){ return n.iota.map!(i => rtype!T()).array; } alias rint = rtypes!int, rlong = rtypes!long, rreal = rtypes!real;
T[][] rtypess(T)(int n, int m){ return n.iota.map!(i => rtypes!T(m)).array; } alias rint = rtypess!int, rlong = rtypess!long, rreal = rtypess!real;

// ----- ----- ----- ----- ----- ----- ----- ----- ----- ----- ----- ----- //

void solve(){
	int n = rint;
	long k = rlong;
	long[] as = rlong(n);
	long[] fs = rlong(n);
	
	log("n:", n, "k:", k, "as:", as, "fs:", fs);
	
	fs.sort!"a<b"();
	as.sort!"a>b"();
	
	bool isOK(long q){
		long xsum;
		foreach(i; 0 .. n){
			long x = min(as[i], q / fs[i]);
			xsum += x;
		}
		if(xsum >= as.sum - k) return 1;
		else return 0;
	}
	
	long ans = downlimit(0, 1_000_000_000_999, &isOK);
	ans.writeln;
}

// 二分探索テンプレート
T uplimit(T)(T a, T c, bool delegate(T) f){
	if(f(c)) return c; if(! f(a)) return a - 1;
	while(a + 1 < c){ T b = (a + c) / 2; if(f(b)) a = b; else c = b; }
	return a;
}
T downlimit(T)(T a, T c, bool delegate(T) f){
	if(f(a)) return a; if(! f(c)) return c + 1;
	while(a + 1 < c){ T b = (a + c) / 2; if(f(b)) c = b; else a = b; }
	return c;
}


