#include <bits/stdc++.h>
using namespace std;
const long long maxN = 1e7 + 5, maxM = 45, mod = 1e9 + 7;
long long N, M;
long long a[maxM], b[maxM], c[maxM];
long long cost;
long long s[maxM];
bool b1[maxM], b0[maxM];
bool cmp(long long i, long long j) { return c[i] < c[j]; }
signed main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  cin >> M >> N;
  long long tot = M * N;
  for (long long i = (long long)0; i <= (long long)M - 1; i++) {
    cin >> a[i];
    a[i + M] = a[i];
  }
  for (long long i = (long long)0; i <= (long long)M - 1; i++) {
    cin >> b[i];
    b[i + M] = b[i];
  }
  M *= 2;
  N /= 2;
  for (long long i = (long long)0; i <= (long long)M - 1; i++) {
    cost += b[i] * N;
    c[i] = a[i] - b[i];
    s[i] = i;
  }
  sort(s, s + M, cmp);
  for (long long rnk = (long long)0; rnk <= (long long)M - 1; rnk++) {
    long long i = s[rnk];
    for (long long j = i + (i & 1); j < M; j += 2) {
      if (!b0[j]) {
        b0[j] = 1;
        cost += c[i];
        break;
      }
    }
    for (long long j = 0; j < M; j += 2) {
      if (!b1[j]) {
        b1[j] = 1;
        cost += c[i] * (N - 1);
        break;
      }
    }
  }
  cout << cost << '\n';
}
