#include <bits/stdc++.h>
using namespace std;
int n, m;
long long a[30], b[30], dp[30][30][30];
struct node {
  long long dis[30][30];
  node operator*(const node &t) const {
    node rep;
    memset(rep.dis, 0x3f, sizeof rep.dis);
    for (int i = 0; i <= n; i++)
      for (int j = 0; j <= n; j++)
        for (int k = 0; k <= n; k++)
          rep.dis[i][j] = min(rep.dis[i][j], dis[i][k] + t.dis[k][j]);
    return rep;
  }
} key;
node pow(node rep, int n) {
  if (n == 1) return rep;
  node req = pow(rep, n / 2);
  if (n % 2 == 0) return req * req;
  return req * req * rep;
}
int main() {
  scanf("%d%d", &n, &m);
  for (int i = 1; i <= n; i++) scanf("%d", &a[i]);
  for (int i = 1; i <= n; i++) scanf("%d", &b[i]);
  memset(dp, 0x3f, sizeof dp);
  for (int i = 0; i <= n; i++) dp[i][i][0] = 0;
  for (int k = 1; k <= n; k++)
    for (int i = 0; i <= n; i++)
      for (int j = 0; j <= n; j++) {
        if (j - 1 >= 0)
          dp[i][j][k] = min(dp[i][j][k], dp[i][j - 1][k - 1] + a[k]);
        if (j + 1 <= n)
          dp[i][j][k] = min(dp[i][j][k], dp[i][j + 1][k - 1] + b[k]);
      }
  for (int i = 0; i <= n; i++)
    for (int j = 0; j <= n; j++) key.dis[i][j] = dp[i][j][n];
  key = pow(key, m);
  printf("%d\n", key.dis[0][0]);
  return 0;
}
