#include <bits/stdc++.h>
using namespace std;
const long long INF = 1234567890123456;
void matmul(const vector<vector<long long> > &A,
            const vector<vector<long long> > &B,
            vector<vector<long long> > &C) {
  int n = A.size();
  for (int i = 0; i < n; ++i) {
    for (int j = 0; j < n; ++j) {
      C[i][j] = INF;
      for (int k = 0; k < n; ++k) {
        C[i][j] = min(C[i][j], A[i][k] + B[k][j]);
      }
    }
  }
}
vector<vector<long long> > ret, A, B, C;
int L[20], R[20];
long long dp[21][41][41];
int n, m;
long long mincost(int pos, int cur, int target) {
  if (cur < 0 || cur > 2 * n) {
    return INF;
  }
  long long &ret = dp[pos][cur][target];
  if (ret != -1) {
    return ret;
  }
  if (pos == n) {
    ret = (cur == target ? 0 : INF);
  } else {
    ret = INF;
    ret = min(ret, L[pos] + mincost(pos + 1, cur + 1, target));
    ret = min(ret, R[pos] + mincost(pos + 1, cur - 1, target));
  }
  return ret;
}
int main() {
  cin >> n >> m;
  for (int i = 0; i < n; ++i) {
    cin >> L[i];
  }
  for (int i = 0; i < n; ++i) {
    cin >> R[i];
  }
  A = vector<vector<long long> >(2 * n + 1, vector<long long>(2 * n + 1));
  ret = B = A;
  memset(dp, 0xff, sizeof dp);
  for (int i = 0; i < 2 * n + 1; ++i) {
    for (int j = 0; j < 2 * n + 1; ++j) {
      A[i][j] = mincost(0, i, j);
    }
  }
  n = 2 * n + 1;
  for (int i = 0; i < n; ++i) {
    for (int j = 0; j < n; ++j) {
      ret[i][j] = INF;
    }
  }
  ret[0][0] = 0;
  while (m > 0) {
    if (m & 1) {
      matmul(ret, A, B);
      ret.swap(B);
    }
    matmul(A, A, B);
    A.swap(B);
    m /= 2;
  }
  cout << ret[0][0] << '\n';
  return 0;
}
