/**
____ ____ ____ ____ ____ ____
||l |||e |||i |||n |||a |||d ||
||__|||__|||__|||__|||__|||__||
|/__\|/__\|/__\|/__\|/__\|/__\|
**/
#include<bits/stdc++.h>
#define endl '\n'
using namespace std;
typedef long long ll;
void speed()
{
ios_base::sync_with_stdio(false);
cin.tie(NULL);
cout.tie(NULL);
}
const ll maxn = 300010;
ll n, m;
ll a[maxn], b[maxn], in[maxn], out[maxn], cp[maxn];
void solve()
{
cin >> n >> m;
bool diff = false;
for (ll i = 1; i <= n; i ++)
cin >> a[i];
for (ll i = 1; i <= n; i ++)
{
cin >> b[i];
if (b[i] != a[i])
diff = true;
}
if (m == 1)
{
ll mx = 1e9;
for (int i = 1; i <= n; i ++)
mx = min(mx, max(a[i], b[i]));
cout << mx << endl;
}
else
if (!diff)
{
double sum = 0;
for (int i = 1; i <= n; i ++)
sum = sum + (double)m / (double)(n) * (double)a[i];
ll lf = 0, rf = ceil(sum);
while(lf <= rf)
{
ll mf = (lf + rf) / 2;
ll nec = 0;
for (int i = 1; i <= n; i ++)
{
nec = nec + mf / a[i];
if (mf % a[i] != 0)
nec ++;
}
if (nec <= n * m)
lf = mf + 1;
else
rf = mf - 1;
}
cout << rf << endl;
}
}
int main()
{
solve();
return 0;
}
