#include <bits/stdc++.h>
#pragma comment(linker, "/STACK:20000000")
using namespace std;
const int SIZE = 128;
const int MAXN = 24;
const long long INF = 1000000000000000000LL;
int n, m;
int open[MAXN], close[MAXN];
long long block[SIZE][SIZE];
int s;
struct Matr {
  long long a[SIZE][SIZE];
};
Matr graph;
Matr Mult(Matr a, Matr b) {
  Matr res;
  for (int i = 0; i < s; i++)
    for (int j = 0; j < s; j++) {
      long long ans = INF;
      for (int u = 0; u < s; u++) ans = min(ans, a.a[i][u] + b.a[u][j]);
      res.a[i][j] = ans;
    }
  return res;
}
Matr Identity() {
  Matr res;
  memset(&res, 63, sizeof(res));
  for (int i = 0; i < s; i++) res.a[i][i] = 0;
  return res;
}
Matr pwr(Matr a, int p) {
  Matr res = Identity();
  Matr x = a;
  for (; p; p >>= 1) {
    if (p & 1) res = Mult(res, x);
    x = Mult(x, x);
  }
  return res;
}
int main() {
  scanf("%d%d", &n, &m);
  for (int i = 0; i < n; i++) scanf("%d", &open[i]);
  for (int i = 0; i < n; i++) scanf("%d", &close[i]);
  memset(block, 63, sizeof(block));
  for (int mask = 0; mask < 1 << n; mask++) {
    int bal = 0;
    int minb = 0;
    int cst = 0;
    for (int i = 0; i < n; i++) {
      if (mask & (1 << i)) {
        bal++;
        cst += open[i];
      } else {
        bal--;
        minb = min(minb, bal);
        cst += close[i];
      }
    }
    auto& num = block[MAXN + bal][-minb];
    if (num > cst) num = cst;
  }
  s = 3 * n + 1;
  memset(&graph, 63, sizeof(graph));
  for (int i = 0; i < s; i++)
    for (int r = 0; r <= i; r++)
      for (int b = -n; b <= n; b++) {
        long long cst = block[MAXN + b][r];
        if (cst > INF) continue;
        auto& num = graph.a[i][i + b];
        num = min(num, cst);
      }
  Matr trans = pwr(graph, m);
  printf("%d\n", int(trans.a[0][0]));
  return 0;
}
