#include <bits/stdc++.h>
using namespace std;
#define int long long
int n,m,a[300005],b[300005],nev[300005];
int nrparti(int x,int y)
{
if (x % y == 0)
return x / y;
return x / y + 1;
}
bool pot(int x)
{
/*int extra = 0;
for (int i = 1; i <= n; i++)
{
nev[i] = x;
if (a[i] <= b[i])
extra += m;
else
{
if (x <= m * a[i])
{
extra += m - nrparti(x,a[i]);
nev[i] = 0;
}
else
{
nev[i] = x - m * a[i];
}
}
}
for (int i = 1; i <= n; i++)
extra -= nrparti(nev[i],b[i]);
if (extra >= 0)
return true;
return false;*/
int op = 0;
for (int i = 1; i <= n; i++)
op += nrparti(x,b[i]);
if (op <= n * m)
return true;
return false;
}
signed main()
{
ios_base::sync_with_stdio(false);
cin.tie(NULL);
cout.tie(NULL);
cin >> n >> m;
for (int i = 1; i <= n; i++)
cin >> a[i];
for (int i = 1; i <= n; i++)
cin >> b[i];
/*int st = 0,pas = 1ll << 60;
while (pas != 0)
{
if (pot(st + pas) == true)
st += pas;
pas /= 2;
}
cout << st;*/
int ans = 1e9;
for (int i = 1; i <= n; i++)
ans = min(ans,max(a[i],b[i]));
cout << ans;
return 0;
}
