#include <bits/stdc++.h>
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx")
using namespace std;
inline bool isDigit(char c) { return '0' <= c && c <= '9'; }
template <class T>
inline T sqr(T x) {
  return x * x;
}
template <class T>
inline bool isSquare(T x) {
  T y = sqrt(x + 0.5);
  return (y * y) == x;
}
template <class T1, class T2>
inline T1 gcd(T1 a, T2 b) {
  return b ? gcd(b, a % b) : a;
}
template <class T1, class T2>
inline T1 eqMin(T1 &x, const T2 &y) {
  if (T1(y) < x) return x = y;
  return x;
}
template <class T1, class T2>
inline T1 eqMax(T1 &x, const T2 &y) {
  if (T1(y) > x) return x = y;
  return x;
}
template <class T1, class T2>
inline T1 min(const T1 &x, const T2 &y) {
  return x < (T1)y ? x : (T1)y;
}
template <class T1, class T2>
inline T1 max(T1 &x, const T2 &y) {
  return x > (T1)y ? x : (T1)y;
}
template <typename T>
inline T getint() {
  T x = 0, p = 1;
  char ch;
  do {
    ch = getchar();
  } while (ch <= ' ');
  if (ch == '-') p = -1, ch = getchar();
  while (ch >= '0' && ch <= '9') x = x * 10 + ch - '0', ch = getchar();
  return x * p;
}
template <class T1, class T2>
ostream &operator<<(ostream &os, const pair<T1, T2> &p) {
  return os << '(' << p.first << ", " << p.second << ')';
}
template <typename T>
auto operator<<(ostream &os, const T &v)
    -> decltype(v.begin(), v.end(), declval<ostream &>()) {
  os << '{';
  bool was = false;
  for (const auto &x : v) {
    if (was) os << ", ";
    was = true;
    os << x;
  }
  os << '}';
  return os;
}
template <size_t sz>
ostream &operator<<(ostream &os, const bitset<sz> &bit) {
  os << '/';
  for (int i = 0; i < sz; i++) os << bit[i];
  os << '\\';
  return os;
}
const double PI = acos(-1);
const double EPS = 1e-8;
const int INF = (int)2e9;
const long long LINF = (long long)2e18;
const int MOD = (int)1e9 + 7;
const int MAXN = (int)1;
int n, m;
vector<long long> s, t;
long long pref = 1, ans;
long long power(long long x, long long step) {
  long long result = 1;
  while (step) {
    if (step & 1) {
      result *= x, result %= MOD;
    }
    x *= x, x %= MOD;
    step >>= 1;
  }
  return result;
}
void input() {
  cin >> n >> m;
  for (int i = 0; i < n; i++) {
    int x;
    cin >> x;
    s.push_back(x);
  }
  for (int i = 0; i < n; i++) {
    int x;
    cin >> x;
    t.push_back(x);
  }
}
int main() {
  ios_base::sync_with_stdio(false);
  input();
  for (int i = 0; i < n; i++) {
    if (s[i] && t[i]) {
      if (s[i] == t[i]) {
        continue;
      }
      ans += (s[i] > t[i]) * pref, ans %= MOD;
      break;
    }
    if (!s[i] && !t[i]) {
      ans += ((((m - 1 + MOD) % MOD) * power((2 * m) % MOD, MOD - 2)) % MOD) *
             pref,
          ans %= MOD;
    } else if (s[i]) {
      ans += (((s[i] - 1) * power(m, MOD - 2)) % MOD) * pref, ans %= MOD;
    } else {
      ans += (((m - t[i]) * power(m, MOD - 2)) % MOD) * pref, ans %= MOD;
    }
    pref *= power(m, MOD - 2), pref %= MOD;
  }
  cout << ans;
}
