#include <bits/stdc++.h> using namespace std; typedef long long ll; int main(){ ll n, m; cin >> n >> m; ll a[n], b[n]; for (ll i = 0; i < n; i ++) cin >> a[i]; for (ll i = 0; i < n; i ++) cin >> b[i]; ll mn = 2e9; for (ll i = 0; i < n; i ++) a[i] = max(a[i], b[i]), mn = min(mn, a[i]); cout << mn << endl; // ll lo = 0, hi = 2e18; // while (hi - lo > 1){ // ll mid = (lo + hi) / 2; // ll rest = 0, del = 0; // for (ll i = 0; i < n; i ++){ // ll need = mid / a[i]; // if (mid % a[i]) need++; // del += min(m, need); // if (need > m){ // ll rem = mid - a[i] * m; // need = rem / b[i]; // if (rem % b[i]) need++; // rest += need; // } // } // if (del + rest <= n * m) // lo = mid; // else // hi = mid; // } // cout << lo << endl; }