#include <bits/stdc++.h>
using namespace std;
int main() {
ios::sync_with_stdio(false);
cin.tie(0);
int n, m;
cin >> n >> m;
vector<int> a(n), b(n);
for (int i = 0; i < n; i++) cin >> a[i];
for (int i = 0; i < n; i++) cin >> b[i];
for (int i = 0; i < n; i++) a[i] = max(a[i], b[i]);
cout << *min_element(a.begin(), a.end()) << '\n';
return 0;
auto check = [&](long long k) {
vector<long long> left(n, k);
long long weeks_left = (long long) n * m;
for (int i = 0; i < n; i++) weeks_left -= (k + a[i] - 1) / a[i];
return weeks_left >= 0;
};
long long lo = 0, hi = (long long) 2e18;
while (lo < hi) {
long long mid = (lo + hi + 1) / 2;
if (check(mid)) lo = mid;
else hi = mid - 1;
}
cout << lo << '\n';
return 0;
}
