//#pragma GCC optimize("O3")
//#pragma GCC target("avx2")
#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
//#define y2 y_2
#define endl '\n'
#define int ll
using namespace std;
using namespace __gnu_pbds;
typedef long long ll;
typedef long double ld;
mt19937 rnd(time(NULL));
const ll mod=998244353;
const int N=600010;
const int Lg=16;
ll a[N],b[N];
ll n,m;
bool ok(ll D){
ll sum=0ll;
for (int i=1;i<=n;i++){
if (a[i]*m>=D){
sum+=m-(D+a[i]-1)/a[i];
} else {
sum-=(D-a[i]*m+b[i]-1)/b[i];
}
}
return (sum>=0);
}
void solve(){
cin>>n>>m;
for (int i=1;i<=n;i++) cin>>a[i];
for (int i=1;i<=n;i++) cin>>b[i];
for (int i=1;i<=n;i++) a[i]=max(a[i],b[i]);
ll ans=0ll;
for (ll i=60;i>=0;i--){
if (ok(ans+(1ll<<i))) ans+=(1ll<<i);
}
cout<<ans<<endl;
}
int32_t main() {
ios_base::sync_with_stdio(false);
cin.tie(0);
int tt=1;
// cin>>tt;
while (tt--){
solve();
}
return 0;
}
