#include <bits/stdc++.h>
using namespace std;
const int N(22), INF(2000000001);
int n, m;
int a[N], b[N];
int g[2 * N][2 * N], ma[2 * N][2 * N], _g[2 * N][2 * N], _ma[2 * N][2 * N];
int cost[N][N];
int bit(int x, int y) { return (x >> y) & 1; }
int main() {
  scanf("%d%d", &n, &m);
  for (int i = int(0); i < int(n); ++i) scanf("%d", &a[i]);
  for (int i = int(0); i < int(n); ++i) scanf("%d", &b[i]);
  for (int i = int(0); i < int(N); ++i)
    for (int j = int(0); j < int(N); ++j) cost[i][j] = INF;
  for (int i = int(0); i < int(1 << n); ++i) {
    int c = 0, c1 = 0, c2 = 0;
    for (int j = int(0); j < int(n); ++j)
      if (bit(i, j)) {
        if (c2)
          --c2;
        else
          ++c1;
        c += b[j];
      } else {
        ++c2;
        c += a[j];
      }
    cost[c1][c2] = min(cost[c1][c2], c);
  }
  for (int i = int(0); i < int(2 * N); ++i)
    for (int j = int(0); j < int(2 * N); ++j) g[i][j] = INF;
  memcpy(ma, g, sizeof(g));
  ma[0][0] = 0;
  for (int i = int(0); i < int(2 * N); ++i)
    for (int j = int(0); j < int(N); ++j)
      for (int k = int(0); k < int(N); ++k)
        if (i >= j && i - j + k < 2 * N)
          g[i][i - j + k] = min(g[i][i - j + k], cost[j][k]);
  for (; m; m /= 2) {
    if (m % 2) {
      for (int i = int(0); i < int(2 * N); ++i)
        for (int j = int(0); j < int(2 * N); ++j) _ma[i][j] = INF;
      for (int i = int(0); i < int(2 * N); ++i)
        for (int j = int(0); j < int(2 * N); ++j)
          for (int k = int(0); k < int(2 * N); ++k)
            _ma[j][k] =
                min((long long)_ma[j][k], (long long)ma[j][i] + g[i][k]);
      memcpy(ma, _ma, sizeof(_ma));
    }
    for (int i = int(0); i < int(2 * N); ++i)
      for (int j = int(0); j < int(2 * N); ++j) _g[i][j] = INF;
    for (int i = int(0); i < int(2 * N); ++i)
      for (int j = int(0); j < int(2 * N); ++j)
        for (int k = int(0); k < int(2 * N); ++k)
          _g[j][k] = min((long long)_g[j][k], (long long)g[j][i] + g[i][k]);
    memcpy(g, _g, sizeof(_g));
  }
  printf("%d\n", ma[0][0]);
  return 0;
}
