#include<bits/stdc++.h> using namespace std; using i64 = long long; int main(){ ios_base::sync_with_stdio(false); cin.tie(NULL); int n; i64 m; cin >> n >> m; vector<i64> a(n); vector<i64> b(n); for(int i = 0;i < n;i++){ cin >> a[i]; } for(int i = 0;i < n;i++){ cin >> b[i]; if(b[i] > a[i]) a[i] = b[i]; } function<bool(i64)> f = [&](i64 x){ i64 have = 0LL; for(int i = 0;i < n;i++){ i64 tot = (x + a[i] - 1LL) / a[i]; if(tot <= m){ have += m - tot; } } for(int i = 0;i < n;i++){ i64 tot = (x + a[i] - 1LL) / a[i]; if(tot > m){ i64 tx = x - m * a[i]; assert(tx >= 0LL); tot = (tx + b[i] - 1LL) / b[i]; assert(tot >= 0); have -= tot; // if(have < 0LL) return false; } } // return true; // return (have >= 0LL); if(have >= 0LL) return true; else return false; }; i64 s = 0; i64 e = (i64)1e18 + 10LL; while(e > s){ i64 mid = (e + s + 1LL) / 2LL; if(f(mid)){ s = mid; }else{ e = mid - 1LL; } } assert(e == s); assert(f(e)); cout << e << '\n'; return 0; }