#include <bits/stdc++.h>
using namespace std;
void check(int &x, int y) {
  if (x == -1 || x > y) x = y;
}
int n, m;
int A[22][22], B[22][22];
int a[22], b[22], dp[22][22];
void cal(int A[][22], int B[][22], int C[][22]) {
  static int ret[22][22];
  for (int i = 0; i < n; i++)
    for (int j = 0; j < n; j++) {
      ret[i][j] = -1;
      for (int k = 0; k < n; k++)
        if (A[i][k] != -1 && B[k][j] != -1) check(ret[i][j], A[i][k] + B[k][j]);
    }
  for (int i = 0; i < n; i++)
    for (int j = 0; j < n; j++) C[i][j] = ret[i][j];
}
int main() {
  scanf("%d%d", &n, &m);
  for (int i = 0; i < n; i++) scanf("%d", &a[i]);
  for (int i = 0; i < n; i++) scanf("%d", &b[i]);
  for (int x = 0; x <= n; x++) {
    memset(dp, -1, sizeof(dp));
    dp[0][x] = 0;
    for (int i = 0; i < n; i++)
      for (int j = 0; j < n + 1; j++)
        if (dp[i][j] != -1) {
          if (j + 1 <= n) {
            check(dp[i + 1][j + 1], dp[i][j] + a[i]);
          }
          if (j - 1 >= 0) check(dp[i + 1][j - 1], dp[i][j] + b[i]);
        }
    for (int y = 0; y < n + 1; y++) A[x][y] = dp[n][y];
  }
  n++;
  for (int i = 0; i < n; i++)
    for (int j = 0; j < n; j++) B[i][j] = i == j ? 0 : -1;
  while (m) {
    if (m & 1) cal(B, A, B);
    cal(A, A, A);
    m >>= 1;
  }
  printf("%d\n", B[0][0]);
  return 0;
}
