#include <bits/stdc++.h>
using namespace std;
#define int long long
#define pi pair<int, int>
#define vi vector<int>
#define vs vector<string>
#define vb vector<bool>
#define vpi vector<pi>
#define pb push_back
#define all(a) (a).begin(), (a).end()
const int mod = 1e9 + 7;
void solve()
{
int n, m;
cin >> n >> m;
int a[n], b[n];
multiset<pi> ms;
for (int i = 0; i < n; i++)
{
cin >> a[i];
ms.insert({m * a[i], a[i]});
}
for (int i = 0; i < n; i++)
cin >> b[i];
for (int k = 0; k < 2 * n; k++)
{
pi sm = *ms.begin();
pi bg = *ms.rbegin();
ms.erase(ms.begin());
ms.erase(prev(ms.end()));
int l = 0;
int r = bg.first / bg.second;
while (l + 1 < r)
{
int md = (l + r) / 2;
if ((md * sm.second) + sm.first > bg.first - (bg.second * md))
{
r = md;
}
else
{
l = md;
}
}
pi p = {(l * sm.second) + sm.first, bg.first - (bg.second * l)};
pi q = {(r * sm.second) + sm.first, bg.first - (bg.second * r)};
if (min(p.first, p.second) == min(q.first, q.second))
{
if (p.first + p.second < q.first + q.second)
{
pi sm2 = {p.first, sm.second};
pi bg2 = {p.second, bg.second};
ms.insert(sm2);
ms.insert(bg2);
}
else
{
pi sm2 = {q.first, sm.second};
pi bg2 = {q.second, bg.second};
ms.insert(sm2);
ms.insert(bg2);
}
}
else if (min(p.first, p.second) > min(q.first, q.second))
{
pi sm2 = {p.first, sm.second};
pi bg2 = {p.second, bg.second};
ms.insert(sm2);
ms.insert(bg2);
}
else
{
pi sm2 = {q.first, sm.second};
pi bg2 = {q.second, bg.second};
ms.insert(sm2);
ms.insert(bg2);
}
}
cout << ms.begin()->first << '\n';
}
signed main()
{
ios_base::sync_with_stdio(0);
cin.tie(NULL);
cout.tie(NULL);
int t = 1;
// cin >> t;
while (t--)
{
solve();
}
return 0;
}
