#include <bits/stdc++.h>
using namespace std;
const double PI = 3.14159265358979;
const double eps = 1e-6;
const long long _INF = 1e18;
const int INF = 1e9;
const int maxn = 50;
const int maxm = 200000;
int n, m;
int a[20], b[20];
long long dp[maxn][maxn];
struct matrix {
  long long ma[maxn][maxn];
} ans;
matrix mul(matrix m1, matrix m2) {
  matrix res;
  for (int i = 0; i < maxn; ++i)
    for (int j = 0; j < maxn; ++j) {
      res.ma[i][j] = _INF;
      for (int k = 0; k < maxn; ++k)
        res.ma[i][j] = (res.ma[i][j] < m1.ma[i][k] + m2.ma[k][j]
                            ? res.ma[i][j]
                            : m1.ma[i][k] + m2.ma[k][j]);
    }
  return res;
}
matrix kpow(matrix m1, int num) {
  matrix res;
  for (int i = 0; i < maxn; ++i) {
    res.ma[i][i] = 0;
    for (int j = 0; j < maxn; ++j)
      if (i != j) res.ma[i][j] = _INF;
  }
  while (num) {
    if (num & 1) res = mul(res, m1);
    m1 = mul(m1, m1);
    num >>= 1;
  }
  return res;
}
int main() {
  while (~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 < maxn; ++i)
      for (int j = 0; j < maxn; ++j) ans.ma[i][j] = _INF;
    for (int k = 0; k < n + 1; ++k) {
      for (int i = 0; i < maxn; ++i)
        for (int j = 0; j < maxn; ++j) dp[i][j] = _INF;
      dp[0][k] = 0;
      for (int i = 0; i < n; ++i)
        for (int j = 0; j < n + 1; ++j) {
          if (j > 0)
            dp[i + 1][j] =
                (dp[i + 1][j] < dp[i][j - 1] + a[i] ? dp[i + 1][j]
                                                    : dp[i][j - 1] + a[i]);
          dp[i + 1][j] =
              (dp[i + 1][j] < dp[i][j + 1] + b[i] ? dp[i + 1][j]
                                                  : dp[i][j + 1] + b[i]);
        }
      for (int i = 0; i < n + 1; ++i) ans.ma[k][i] = dp[n][i];
    }
    printf("%I64d\n", kpow(ans, m).ma[0][0]);
  }
  return 0;
}
