#include <cstdio>
#include <cstdlib>
#include <algorithm>
#include <vector>
#include <cstring>
#include <queue>
#include <set>
#include <unordered_set>
#include <unordered_map>
#include <map>
#include <numeric>
#include <functional>
#include <cmath>
#include <cassert>
#include <string>
#include <iostream>

using namespace std;
typedef long long ll;
typedef pair<int, int> P;
typedef pair<ll, ll> PL;
const ll MOD = 1000000007;
const int mod = 1000000007;
ll INF = 1LL << 60;


template <typename T>
istream &operator>>(istream &is, vector<T> &vec)
{
   for (auto &v : vec)
      is >> v;
   return is;
}
template <typename T>
ostream &operator<<(ostream &os, const vector<T> &vec)
{
   os << "[";
   for (auto v : vec)
      os << v << ",";
   os << "]";
   return os;
}
template <typename T>
ostream &operator<<(ostream &os, const deque<T> &vec)
{
   os << "deq[";
   for (auto v : vec)
      os << v << ",";
   os << "]";
   return os;
}
template <typename T>
ostream &operator<<(ostream &os, const set<T> &vec)
{
   os << "{";
   for (auto v : vec)
      os << v << ",";
   os << "}";
   return os;
}
template <typename T>
ostream &operator<<(ostream &os, const unordered_set<T> &vec)
{
   os << "{";
   for (auto v : vec)
      os << v << ",";
   os << "}";
   return os;
}
template <typename T>
ostream &operator<<(ostream &os, const multiset<T> &vec)
{
   os << "{";
   for (auto v : vec)
      os << v << ",";
   os << "}";
   return os;
}
template <typename T>
ostream &operator<<(ostream &os, const unordered_multiset<T> &vec)
{
   os << "{";
   for (auto v : vec)
      os << v << ",";
   os << "}";
   return os;
}
template <typename T1, typename T2>
ostream &operator<<(ostream &os, const pair<T1, T2> &pa)
{
   os << "(" << pa.first << "," << pa.second << ")";
   return os;
}
template <typename TK, typename TV>
ostream &operator<<(ostream &os, const map<TK, TV> &mp)
{
   os << "{";
   for (auto v : mp)
      os << v.first << "=>" << v.second << ",";
   os << "}";
   return os;
}
template <typename TK, typename TV>
ostream &operator<<(ostream &os, const unordered_map<TK, TV> &mp)
{
   os << "{";
   for (auto v : mp)
      os << v.first << "=>" << v.second << ",";
   os << "}";
   return os;
};
#define dbg(x) cerr << #x << " = " << (x) << " (L" << __LINE__ << ") " << __FILE__ << endl;
template <typename A, size_t N, typename T>
void Fill(A (&array)[N], const T &val)
{
   fill((T *)array, (T *)(array + N), val);
}





ll a[202020], f[202020];
ll n, k;
bool ok(ll v){
   ll cnt = 0;
   for(int i=0; i < n; i++){
      ll t = a[i] * f[i];
      if(v - t >= 0)continue;

      cnt += a[i] - (v / f[i]);

   }
   if(cnt <= k){
      return true;
   }else{
      return false;
   }
}

int solve()
{
   cin >> n >> k;
   for(int i=0; i < n; i++){
      cin >> a[i];
   }
   for(int i=0; i < n; i++){
      cin >> f[i];
   }
   sort(a, a + n);
   sort(f, f + n,greater<ll>());
   ll l=0,r= 1LL << 60;
   ll m;
   for(int i=0; i < 200; i++){
      m = (l + r) / 2;
      if(ok(m)){
         r = m;
      }else{
         l = m;
      }
   }

   cout << r << endl;

   return 0;
}
int main()
{
   //cout.precision(10)
   ios::sync_with_stdio(false);
   cin.tie(0);

   solve();
}

Measured memory_bytes: 3456