#include <bits/stdc++.h>
using namespace std;
long long i, j, k, l, n, m, sum, an, K;
const long long N = 51;
long long va[N], vb[N];
typedef long long arr[N][N];
arr a, b, c, d;
void cheng(arr &a, arr b) {
  memset(c, 2, sizeof(c));
  for (long long i = 0; i <= K; i++)
    for (long long j = 0; j <= K; j++)
      for (long long k = 0; k <= K; k++)
        c[i][j] = min(c[i][j], a[i][k] + b[k][j]);
  memcpy(a, c, sizeof(a));
}
int main() {
  scanf("%I64d%I64d", &n, &m);
  K = 2 * n;
  for (long long i = 1; i <= n; i++) scanf("%I64d", &va[i]), va[n + i] = va[i];
  for (long long i = 1; i <= n; i++) scanf("%I64d", &vb[i]), vb[n + i] = vb[i];
  memset(b, 2, sizeof(b));
  for (long long i = 0; i <= K; i++) b[i][i] = 0;
  for (long long i = 1; i <= K; i++) {
    memset(d, 2, sizeof(d));
    for (long long j = 0; j <= K; j++) {
      if (j + 1 <= K) d[j][j + 1] = va[i];
      if (j) d[j][j - 1] = vb[i];
    }
    cheng(b, d);
  }
  memset(a, 2, sizeof(a));
  a[0][0] = 0;
  m /= 2;
  while (m) {
    if (m & 1) cheng(a, b);
    cheng(b, b);
    m /= 2;
  }
  printf("%I64d\n", a[0][0]);
  return 0;
}
