#include <bits/stdc++.h>
using namespace ::std;
const long double PI = acos(-1);
const long long MOD = 1000000000 + 7;
long long gcd(long long a, long long b) { return b == 0 ? a : gcd(b, a % b); }
long long add(long long a, long long b, long long m = MOD) {
  return (a % m + b % m + 2 * m) % m;
}
long long mul(long long a, long long b, long long m = MOD) {
  return ((a % m + m) * (b % m + m)) % m;
}
long long pow_mod(long long a, long long b, long long m = MOD) {
  long long res = 1LL;
  a = a % m;
  while (b) {
    if (b & 1) res = mul(res, a, m);
    b >>= 1;
    a = mul(a, a, m);
  }
  return res;
}
long long fastexp(long long a, long long b) {
  long long res = 1LL;
  while (b) {
    if (b & 1) res = res * a;
    b >>= 1;
    a *= a;
  }
  return res;
}
int gcdExtendido(int a, int b, int *x, int *y) {
  if (a == 0) {
    *x = 0;
    *y = 1;
    return b;
  }
  int x1, y1;
  int gcd = gcdExtendido(b % a, a, &x1, &y1);
  *x = y1 - (b / a) * x1;
  *y = x1;
  return gcd;
}
int modInverso(int a, int m) {
  int x, y;
  int g = gcdExtendido(a, m, &x, &y);
  if (g != 1)
    return -1;
  else
    return (x % m + m) % m;
}
const int N = 20 + 5;
const int E = 40 + 5;
const long long inf = 1LL << 40;
int n, m, p;
int a[N];
int b[N];
long long M[E][E];
long long r[E][E];
void compute_balance(vector<vector<long long> > &memo, int x) {
  for (int i = 0; i <= n; i++) {
    for (int j = 0; j <= p; j++) memo[i][j] = 1LL << 32;
  }
  memo[0][x] = 0;
  for (int i = 1; i <= n; i++) {
    for (int j = 0; j <= p; j++) {
      if (j) memo[i][j] = min(memo[i][j], memo[i - 1][j - 1] + 1LL * a[i - 1]);
      if (j + 1 <= p)
        memo[i][j] = min(memo[i][j], memo[i - 1][j + 1] + 1LL * b[i - 1]);
    }
  }
}
void preprocess() {
  vector<vector<long long> > memo;
  memo.resize(n + 1);
  for (int i = 0; i <= n; i++) memo[i].resize(p + 1);
  for (int initial_balance = 0; initial_balance <= p; initial_balance++) {
    compute_balance(memo, initial_balance);
    for (int i = 0; i <= p; i++) {
      M[initial_balance][i] = memo[n][i];
    }
  }
}
void multiply(long long a[][E], long long b[][E]) {
  long long c[E][E];
  for (int i = 0; i <= p; i++) {
    for (int j = 0; j <= p; j++) {
      c[i][j] = 1LL << 32;
      for (int k = 0; k <= p; k++) {
        c[i][j] = min(c[i][j], a[i][k] + b[k][j]);
      }
    }
  }
  for (int i = 0; i <= p; i++)
    for (int j = 0; j <= p; j++) a[i][j] = c[i][j];
}
long long fast_expo() {
  for (int i = 0; i <= p; i++) {
    for (int j = 0; j <= p; j++) {
      r[i][j] = i == j ? 0 : 1LL << 32;
    }
  }
  long long A[E][E];
  for (int i = 0; i <= p; i++)
    for (int j = 0; j <= p; j++) A[i][j] = M[i][j];
  while (m) {
    if (m & 1) {
      multiply(r, A);
    }
    m >>= 1;
    multiply(A, A);
  }
  return r[0][0];
}
int main() {
  scanf("%d %d", &(n), &(m));
  p = 2 * n;
  for (int i = 0; i < n; i++) {
    scanf("%d", &(a[i]));
  }
  for (int i = 0; i < n; i++) {
    scanf("%d", &(b[i]));
  }
  preprocess();
  printf("%lld\n", fast_expo());
  return 0;
}
