/*input
4 1
7 6 4 5
9 8 3 3
*/
#include<bits/stdc++.h>
using namespace std;
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace __gnu_pbds;
typedef tree<long long, null_type, less_equal<long long>, rb_tree_tag, tree_order_statistics_node_update> indexed_set;
#pragma GCC optimize("unroll-loops,no-stack-protector")
//order_of_key #of elements less than x
// find_by_order kth element
using ll = long long;
using ld = long double;
using pii = pair<int,int>;
#define f first
#define s second
#define pb push_back
#define REP(i,n) for(int i=0;i<n;i++)
#define REP1(i,n) for(int i=1;i<=n;i++)
#define FILL(n,x) memset(n,x,sizeof(n))
#define ALL(_a) _a.begin(),_a.end()
#define sz(x) (int)x.size()
#define SORT_UNIQUE(c) (sort(c.begin(),c.end()), c.resize(distance(c.begin(),unique(c.begin(),c.end()))))
const ll INF64=4e18;
const int INF=0x3f3f3f3f;
const ll MOD=1e9+7;
const ld PI=acos(-1);
const ld eps=1e-6;
#define lowb(x) x&(-x)
#define MNTO(x,y) x=min(x,(__typeof__(x))y)
#define MXTO(x,y) x=max(x,(__typeof__(x))y)
ll sub(ll a,ll b){
ll x=a-b;
while(x<0) x+=MOD;
while(x>MOD) x-=MOD;
return x;
}
ll mult(ll a,ll b){
return (a*b)%MOD;
}
ll mypow(ll a,ll b){
if(b<=0) return 1;
ll res=1LL;
while(b){
if(b&1) res=(res*a)%MOD;
a=(a*a)%MOD;
b>>=1;
}
return res;
}
const ll maxn=5e5+5;
const ll maxlg=__lg(maxn)+2;
ll a[maxn],b[maxn];
ll n,m;
bool wk(ll mid){
__int128 tot=0;
REP(i,n){
if(a[i]==b[i]){
tot+=m;
tot-=(mid+b[i]-1)/b[i];
continue;
}
ll free=(m-((mid+a[i]-1)/a[i]));
if(free<0) tot-=(mid-1LL*m*a[i]+b[i]-1)/b[i];
else tot+=free;
}
return tot>=0;
}
int main(){
cin>>n>>m;
REP(i,n) cin>>a[i];
REP(i,n) cin>>b[i],MXTO(a[i],b[i]);
ll l=0,r=INF64;
while(l<r){
ll mid=(l+r+1)/2;
if(wk(mid)) l=mid;
else r=mid-1;
}
cout<<l;
}
