#include <bits/stdc++.h>
using namespace std;
bool is_prime(long long n) {
  for (long long i = 2; i * i <= n; ++i) {
    if (n % i == 0) {
      return false;
    }
  }
  return true;
}
vector<long long> fact(long long n) {
  n = abs(n);
  vector<long long> ans;
  for (int i = 1; i * i <= n; i++) {
    if (n % i == 0) {
      ans.push_back(i);
      ans.push_back(n / i);
    }
  }
  return ans;
}
inline long long getPow(long long a, long long b) {
  long long res = 1ll, tp = a;
  while (b) {
    if (b & 1ll) {
      res *= tp;
      res %= 1000000007;
    }
    tp *= tp;
    tp %= 1000000007;
    b >>= 1ll;
  }
  return res;
}
long long vec_mult(const pair<long long, long long>& t1,
                   const pair<long long, long long>& t2,
                   const pair<long long, long long>& t3) {
  const long long &x1 = t1.first, y1 = t1.second;
  const long long &x2 = t2.first, y2 = t2.second;
  const long long &x3 = t3.first, y3 = t3.second;
  return abs((x2 - x1) * (y3 - y1) - (y2 - y1) * (x3 - x1));
}
void ok() {
  cout << "YES" << endl;
  exit(0);
}
void no() {
  cout << "NO" << endl;
  exit(0);
}
inline long long nxt() {
  long long x;
  cin >> x;
  return x;
}
const long long N = 2e5 + 5, inf = 1e18;
int days[13] = {0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0), cout.tie(0);
  long long n = nxt(), m = nxt();
  long long te1 = 0;
  long long te2 = 0;
  for (int i = 1; i <= m; i++) {
    long long cur = getPow(m, 1000000007 - 2) % 1000000007 * (i - 1) %
                    1000000007 * getPow(m, 1000000007 - 2) % 1000000007;
    te1 += cur;
    te1 %= 1000000007;
  }
  for (int i = 1; i <= m; i++) {
    te2 += getPow(m, 1000000007 - 2) * getPow(m, 1000000007 - 2) % 1000000007;
    te2 %= 1000000007;
  }
  vector<long long> a(n);
  vector<long long> b(n);
  for (int i = 0; i < n; i++) {
    a[i] = nxt();
  }
  for (int i = 0; i < n; i++) {
    b[i] = nxt();
  }
  long long ans = 0;
  long long t = 1ll;
  for (int i = 0; i < n; i++) {
    if (a[i] == 0) {
      if (b[i] == 0) {
        ans += t * te1 % 1000000007;
      } else {
        long long tmp = m - b[i];
        ans += t * tmp % 1000000007 * getPow(m, 1000000007 - 2) % 1000000007;
      }
    } else {
      if (b[i] == 0) {
        long long tmp = a[i] - 1;
        ans += t * tmp % 1000000007 * getPow(m, 1000000007 - 2) % 1000000007;
      } else {
        if (a[i] > b[i]) {
          ans += t;
          break;
        }
      }
    }
    if (a[i] == 0 && b[i] == 0) {
      t *= te2;
    } else if (a[i] == 0 && b[i]) {
      t *= getPow(m, 1000000007 - 2);
    } else if (a[i] && b[i] == 0) {
      t *= getPow(m, 1000000007 - 2);
    } else if (a[i] && b[i]) {
      if (a[i] < b[i]) {
        t = 0;
      }
    }
    t %= 1000000007;
    ans %= 1000000007;
  }
  cout << ans % 1000000007;
  return 0;
}
