#include <bits/stdc++.h>
using namespace std;
const int MAXN = 20;
long long int mat[MAXN + 1][MAXN + 1];
long long int res[MAXN + 1][MAXN + 1];
long long int aux[MAXN + 1][MAXN + 1];
void mul(long long int a[MAXN + 1][MAXN + 1],
         long long int b[MAXN + 1][MAXN + 1],
         long long int c[MAXN + 1][MAXN + 1], int n) {
  for (int i = 0; i <= n; i++) {
    for (int j = 0; j <= n; j++) {
      aux[i][j] = ((long long int)1e15);
    }
  }
  for (int i = 0; i <= n; i++) {
    for (int j = 0; j <= n; j++) {
      for (int k = 0; k <= n; k++) {
        aux[i][j] = min(aux[i][j], b[i][k] + c[k][j]);
      }
    }
  }
  for (int i = 0; i <= n; i++) {
    for (int j = 0; j <= n; j++) {
      a[i][j] = aux[i][j];
    }
  }
  return;
}
void fast_exp(int n, int p) {
  for (int i = 0; i <= n; i++) {
    for (int j = 0; j <= n; j++) {
      res[i][j] = mat[i][j];
    }
  }
  while (p > 0) {
    if (p & 1) {
      mul(res, res, mat, n);
    }
    mul(mat, mat, mat, n);
    p /= 2;
  }
  return;
}
int main(void) {
  int n, m;
  int a[MAXN];
  int b[MAXN];
  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 i = 0; i <= n; i++) {
    for (int j = 0; j <= n; j++) {
      mat[i][j] = ((long long int)1e15);
    }
  }
  for (int mask = 0; mask < 1 << n; mask++) {
    int bal = 0;
    int cost = 0;
    int mini = 0;
    for (int i = 0; i < n; i++) {
      int bit = (mask >> i) & 1;
      if (bit) {
        cost += a[i];
        bal++;
      } else {
        cost += b[i];
        bal--;
      }
      mini = min(mini, bal);
    }
    for (int i = 0; i <= n; i++) {
      if (0 <= i + bal && i + bal <= n && i + mini >= 0) {
        mat[i][i + bal] = min(mat[i][i + bal], 1LL * cost);
      }
    }
  }
  fast_exp(n, m - 1);
  printf("%lld\n", res[0][0]);
  return 0;
}
