/*
IN THE NAME OF GOD
*/
#include <bits/stdc++.h>
// #pragma GCC target("avx2,bmi,bmi2,lzcnt,popcnt")
// #pragma GCC optimize("O3")
// #pragma GCC optimize("unroll-loops")
using namespace std;
typedef __int128 ll;
typedef pair<ll, ll> pll;
typedef pair<int, int> pii;
typedef long double ld;
#define F first
#define S second
#define Mp make_pair
#define pb push_back
#define pf push_front
#define size(x) ((ll)x.size())
#define all(x) (x).begin(),(x).end()
#define kill(x) cout << x << '\n', exit(0);
#define fuck(x) cout << "(" << #x << " , " << x << ")" << endl
#define endl '\n'
const int N = 3e5+23, lg = 18;
ll Mod = 1e9+7; //998244353;
inline ll MOD(ll a, ll mod=Mod) {a%=mod; (a<0)&&(a+=mod); return a;}
inline ll poww(ll a, ll b, ll mod=Mod) {
ll ans = 1;
a=MOD(a, mod);
while (b) {
if (b & 1) ans = MOD(ans*a, mod);
b >>= 1;
a = MOD(a*a, mod);
}
return ans;
}
long long nn, mm, A[N], B[N];
ll n, m, a[N], b[N];
int main () {
ios_base::sync_with_stdio(false), cin.tie(0);
cin>>nn>>mm;
for(int i=1; i<=nn; i++) cin>>A[i];
for(int i=1; i<=nn; i++) cin>>B[i];
n=nn, m=mm;
for(int i=1; i<=n; i++) a[i]=A[i], b[i]=B[i];
ll l=0, r=1e18+1;
while(r-l > 1) {
ll mid = (l+r)/2;
ll num = 0, yey = 1;
for(int i=1; i<=n; i++) {
if(a[i] >= b[i]) {
num -= max((ll)0, m - ((mid+a[i]-1)/a[i]));
num += max((ll)0, ((mid-m*a[i]+b[i]-1)/b[i]));
} else {
num -= max((ll)0, m - ((mid+b[i]-1)/b[i]));
num += max((ll)0, ((mid-m*b[i]+b[i]-1)/b[i]));
}
}
if(num <= (ll)0) l=mid;
else r=mid;
}
cout<<(long long)l<<endl;
return 0;
}
