#include <bits/stdc++.h>
using namespace std;
const long long INF = 1000000000000000000;
vector<long long> add1(vector<long long> x, vector<long long> d){
  int K = d.size();
  vector<long long> ans(K);
  ans[0] = min(d[0], x[K - 1]);
  for (int i = 1; i < K; i++){
    ans[i] = max(x[i - 1], min(d[i], x[K - 1]));
  }
  return ans;
}
vector<long long> mul2(vector<long long> x, vector<long long> d){
  int K = d.size();
  vector<vector<long long>> next(K);
  next[0] = x;
  for (int i = 1; i < K; i++){
    next[i] = add1(next[i - 1], d);
  }
  vector<long long> ans(K, -INF);
  for (int i = 0; i < K; i++){
    for (int j = 0; j < K; j++){
      ans[j] = max(ans[j], min(next[i][j], x[i]));
    }
  }
  return ans;
}
int main(){
  int K;
  long long N;
  cin >> K >> N;
  vector<long long> A(K);
  for (int i = 0; i < K; i++){
    cin >> A[i];
  }
  vector<long long> B(K);
  for (int i = 0; i < K; i++){
    cin >> B[i];
  }
  vector<long long> C(K, -INF);
  C[0] = INF;
  for (int i = 60; i >= 0; i--){
    C = mul2(C, B);
    if ((N >> i & 1) == 1){
      C = add1(C, B);
    }
  }
  long long ans = -INF;
  for (int i = 0; i < K; i++){
    ans = max(ans, min(A[i], C[i]));
  }
  cout << ans << endl;
}