#include <bits/stdc++.h> #define int long long using namespace std; using idata = vector<int>; int N, M; idata As, Bs; int solve (int A, int B, int target) { if (A < B) A = B; if (A * M >= target) return M - ceil(((double) target) / ((double) A)); int local = target - A * M; return - ceil(((double)local) / ((double) B)); } bool check (int target) { int res = 0; for (int i = 0; i < N; i ++) res += solve(As[i], Bs[i], target); return res >= 0; } signed main () { cin >> N >> M; As.resize(N); Bs.resize(N); for (int i = 0; i < N; i ++) cin >> As[i]; for (int i = 0; i < N; i ++) cin >> Bs[i]; int a = 0; int b = 1e18; while (b - a > 1) { int c = (a + b) >> 1; if (check(c)) a = c; else b = c; } cout << a << endl; }