#include <bits/stdc++.h>
#include <fstream>
using namespace std;
template<class A, class B>
ostream& operator<<(ostream& o, const pair<A, B>& p) {return o << '(' << p.first << ", " << p.second << ')';}
template<size_t Index = 0, typename... Types>
ostream& printTupleElements(ostream& o, const tuple<Types...>& t) {if constexpr (Index < sizeof...(Types)){if(Index > 0){o << ", ";}o << get<Index>(t);printTupleElements<Index + 1>(o, t);}return o;}
template<typename... Types>
ostream& operator<<(ostream& o, const tuple<Types...>& t){o << "(";printTupleElements(o, t);return o << ")";}
template<class T>
auto operator<<(ostream& o, const T& x) -> decltype(x.end(), o){o << '{';bool first = true;for (const auto& e : x){if (!first){o << ", ";}o << e;first = false;} return o << '}';}
#define DEBUG
#ifdef DEBUG
#define fastio()
#define debug(x...) cerr << "[" #x "]: ", [](auto... $) {((cerr << $ << "; "), ...); }(x), cerr << '\n'
#define check(x) if (!(x)) { cerr << "Check failed: " << #x << " in line " << __LINE__ << endl; exit(1); }
#else
#define fastio() ios_base::sync_with_stdio(0); cin.tie(0);
#define debug(...)
#define check(x)
#endif
typedef long long ll;
#define pi pair<int, int>
#define pl pair<ll, ll>
#define st first
#define nd second
#define vi vector<int>
#define vll vector<ll>
#define eb emplace_back
#define all(x) (x).begin(), (x).end()
#define sz(x) (int)(x).size()
constexpr int LIM = 3e5;
ll A[LIM + 10];
ll B[LIM + 10];
bool czy(ll x, int n, ll m) {
ll wol = 0;
for(int i = 1; i <= n; i++) {
if(A[i] * m >= x) {
wol += m - ((x + A[i] - 1) / A[i]);
}
else {
wol -= ((x - A[i] * m) + B[i] - 1) / B[i];
}
if(wol + (ll)n * m < 0) {
return 0;
}
}
return wol >= 0;
}
void solve() {
//ifstream cin("nazwa.in");
//ofstream cout("nazwa.out");
int n, m;
cin >> n >> m;
for(int i = 1; i <= n; i++) {
cin >> A[i];
}
for(int i = 1; i <= n; i++) {
cin >> B[i];
A[i] = max(A[i], B[i]);
}
ll l = 0;
ll r = 1e18;
while(l < r) {
ll mid = (l + r + 1) / 2;
if(czy(mid, n, m)) {
l = mid;
}
else {
r = mid - 1;
}
}
cout << l << '\n';
}
int main() {
fastio();
int t;
//cin >> t;
t = 1;
while(t--) {
solve();
}
}
