#include <bits/stdc++.h>
using namespace std;
#define int long long
#define FOR(i,a,b) for (int i = (a); i < (b); ++i)
#define pb push_back
#define all(a) a.begin(), a.end()
#define endl "\n"
void printVector(vector<int> a){
for (auto x: a) cout << x << " ";
cout << endl;
}
void solve(){
int n, m; cin >> n >> m;
vector<int> a(n);
FOR(i,0,n) cin >> a[i];
vector<int> b(n);
FOR(i,0,n) cin >> b[i];
int l = 1; int r = 1e18;
int ans = 0;
while (l < r){
int mid = (l+r)/2;
int tot = 0;
FOR(i,0,n){
tot += (mid+a[i]-1)/a[i];
}
if (tot <= n*m){
ans = max(ans, mid);
l = mid+1;
}else{
r = mid-1;
}
}
cout << ans << endl;
}
int32_t main(){
ios::sync_with_stdio(false);cin.tie(nullptr);
int t = 1; // cin >> t;
while (t--) solve();
}
