#include "bits/stdc++.h"
using namespace std;
#define ll long long
#define ln '\n'
const int N = 3e5 + 5;
const ll INF = 3e15 + 5;
ll n, m, a[N], b[N];
inline ll ceil(ll x, ll y) {return (x + y - 1) / y;}
void solve(){
cin >> n >> m;
for (int i = 0; i < n; i++) cin >> a[i];
for (int i = 0; i < n; i++) cin >> b[i];
// ll l = 25, r = 25, ans = 0;
ll l = 0, r = INF, ans = 0;
while (l <= r){
ll tar = (l + r) / 2;
ll free, need; free = need = 0;
for (int i = 0; i < n; i++){
if (b[i] >= a[i]) {
free += max(0LL, m - ceil(tar, b[i]));
need += max(0LL, ceil(tar, b[i]) - m);
} else {
ll go_lesson = min(m, ceil(tar, a[i]));
need += max(0LL, ceil(tar - a[i] * go_lesson, b[i]));
free += max(0LL, m - go_lesson);
}
// cout << need << ' ' << free << ln;
}
if (need <= free) {ans = tar; l = tar + 1;}
else r = tar - 1;
}
cout << ans << ln;
}
int main() {
ios_base::sync_with_stdio(false);
cin.tie(NULL);
// int TT; cin >> TT;
// while (TT--) {solve();}
solve();
}
