#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define st first
#define nd second
#define pb push_back
#define all(a) a.begin(), a.end()
const ll I = 1000000LL * 1000000LL * 1000000LL + 2LL;
const int N = 3 * 100 * 1000 + 7;
ll a[N], b[N];
ll Bal(ll m, int v, ll x)
{
if(b[v] >= a[v])
return m - ((x + b[v] - 1) / b[v]);
if(m * a[v] >= x)
return m - ((x + a[v] - 1) / a[v]);
return -((x - a[v] * m + b[v] - 1) / b[v]);
}
bool Check(int n, ll m, ll x)
{
ll l = 0;
for(int i = 1; i <= n; ++i)
{
l += Bal(m, i, x);
if(l < -I)
return false;
}
return (l >= 0);
}
ll BS(int n, ll m)
{
ll p = 0LL, k = I, s;
while(p < k)
{
s = (p + k + 1) / 2;
if(Check(n, m, s))
p = s;
else
k = s - 1;
}
return p;
}
void Solve()
{
int n; ll m;
cin >> n >> m;
for(int i = 1; i <= n; ++i)
cin >> a[i];
for(int i = 1; i <= n; ++i)
cin >> b[i];
cout << BS(n, m) << "\n";
}
int main()
{
ios_base::sync_with_stdio(false);
cin.tie(nullptr);
Solve();
return 0;
}
