#include <bits/stdc++.h>
using namespace std;
const int max_n = 128;
const int max_lgm = 30;
typedef long long mat[3 * max_n][3 * max_n];
const long long inf = 1000000000000000LL;
int n, m;
long long a[max_n], b[max_n];
mat cur, nxt, pow2[max_lgm];
mat tmp, ans;
void prod(mat a, mat b, mat res) {
  for (int i = 0; i <= 3 * n; i++)
    for (int j = 0; j <= 3 * n; j++) {
      long long val = inf;
      for (int k = 0; k <= 3 * n; k++) val = min(val, a[i][k] + b[k][j]);
      res[i][j] = val;
    }
}
int main() {
  scanf("%d %d", &n, &m);
  for (int i = 0; i < n; i++) scanf("%lld", &a[i]);
  for (int i = 0; i < n; i++) scanf("%lld", &b[i]);
  for (int i = 0; i <= 3 * n; i++)
    for (int j = 0; j <= 3 * n; j++) cur[i][j] = (i == j) ? 0LL : inf;
  for (int i = 0; i < n; i++) {
    for (int j = 0; j <= 3 * n; j++)
      for (int k = 0; k <= 3 * n; k++) nxt[j][k] = inf;
    for (int j = 0; j <= 3 * n; j++)
      for (int k = 0; k <= 3 * n; k++) {
        if (0 < k) nxt[j][k - 1] = min(nxt[j][k - 1], cur[j][k] + b[i]);
        if (k < 3 * n) nxt[j][k + 1] = min(nxt[j][k + 1], cur[j][k] + a[i]);
      }
    for (int j = 0; j <= 3 * n; j++)
      for (int k = 0; k <= 3 * n; k++) cur[j][k] = nxt[j][k];
  }
  for (int i = 0; i <= 3 * n; i++)
    for (int j = 0; j <= 3 * n; j++) pow2[0][i][j] = cur[i][j];
  for (int i = 0; i < max_lgm - 1; i++) prod(pow2[i], pow2[i], pow2[i + 1]);
  for (int i = 0; i <= 3 * n; i++)
    for (int j = 0; j <= 3 * n; j++) ans[i][j] = (i == j) ? 0LL : inf;
  for (int i = 0; i < max_lgm; i++)
    if (m & (1 << i)) {
      prod(pow2[i], ans, tmp);
      for (int j = 0; j <= 3 * n; j++)
        for (int k = 0; k <= 3 * n; k++) ans[j][k] = tmp[j][k];
    }
  printf("%lld\n", ans[0][0]);
  return 0;
}
