#include <bits/stdc++.h>
using namespace std;
long long a, b, c, d, e, f, g[25], h[25], i, j, k;
void Inf(long long x[25][25]) {
  for (long long ii = 0; ii < 25; ii++)
    for (long long jj = 0; jj < 25; jj++) x[ii][jj] = (1LL << 60);
  ;
}
struct node {
  long long x[25][25];
  friend node operator+(const node &x, const node &y) {
    long long ii, jj, kk;
    node R;
    Inf(R.x);
    for (ii = 0; ii <= a; ii++)
      for (jj = 0; jj <= a; jj++) {
        for (kk = 0; kk <= a; kk++)
          R.x[ii][jj] = min(R.x[ii][jj], x.x[ii][kk] + y.x[kk][jj]);
      }
    return R;
  }
};
node Root, F;
node Make_Matrix(long long x) {
  long long ii, jj, kk;
  node R;
  Inf(R.x);
  for (ii = 0; ii <= a; ii++) {
    if (ii + 1 <= a) R.x[ii][ii + 1] = g[x];
    if (ii - 1 >= 0) R.x[ii][ii - 1] = h[x];
  }
  return R;
}
node Mi(node x, long long y) {
  long long ii, jj, kk;
  node R;
  if (y == 1) return x;
  R = Mi(x, y >> 1);
  R = R + R;
  if (y & 1) R = R + x;
  return R;
}
int main() {
  cin >> a >> b;
  for (i = 1; i <= a; i++) cin >> g[i];
  for (i = 1; i <= a; i++) cin >> h[i];
  Root = Make_Matrix(1);
  for (i = 2; i <= a; i++) Root = Root + Make_Matrix(i);
  F = Mi(Root, b);
  cout << F.x[0][0] << endl;
  return 0;
}
