//g++ filename.cpp -std=c++14 -DH
#ifdef H
#include "/Users/michaelw/stdc++.h"
#else
#include <bits/stdc++.h>
#endif

using namespace std;

#define endl '\n'
#define pb push_back
#define f first
#define s second
#define lb lower_bound
#define ub upper_bound
#define all(x) x.begin(), x.end()
#define pq priority_queue

typedef long long ll;
typedef pair<int, string> pis;
typedef pair<int,int> pii;

const ll MOD = 1000000007;

ll GCD(ll a, ll b)
{
   if (b==0) return a;

   return GCD(b,a%b);
}

void reduce_fraction(ll &num, ll&denom){
    ll both = GCD(num, denom);
    num /= both;
    denom /= both;
}
ll realMod(ll num, ll denom, ll MOD){
    for(int i = 0; ; i++){
        if((num + MOD*i) % denom == 0){
            return (num + MOD*i) / denom;
        }
    }
}

int main(){
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    ifstream fin("filename.in");
    ofstream fout("filename.out");
    ll n, m;
    cin >> n >> m;
    ll prob = 0;
    ll num = 1, denom = 1;
    bool weird = 0;
    vector<int> s1 (n), s2 (n);
    for(int i = 0; i < n; i++){
        cin >> s1[i];
    }
    for(int i = 0; i < n; i++){
        cin >> s2[i];
    }
    for(int i = 0; i < n; i++){
        if(s1[i] != 0 && s2[i] != 0){
            if(s1[i] > s2[i]){
                reduce_fraction(num, denom);
                if(denom == 1) cout << 1 << endl;
                // cout << num << " " << denom << endl;
                else cout << prob + << endl;
                return 0;
            }
            else if(s2[i] > s1[i]){
                reduce_fraction(num, denom);
                if(denom == 1){
                    cout << 0 << endl;
                }
                else{
                    cout << prob << endl;
                }
                return 0;
            }
        }
        else if(s1[i] == 0 && s2[i] != 0){
            num *= (m-s2[i]);
            num %= MOD;
            denom *= m;
            denom %= MOD;
            reduce_fraction(num, denom);
            prob += realMod(num, denom, MOD);
            num = 1;
            denom = m;
            // prob *= (m-s2[i]) / m % MOD;
        }
        else if(s1[i] != 0 && s2[i] == 0){
            num *= s1[i]-1;
            num %= MOD;
            denom *= m;
            denom %= MOD;
            reduce_fraction(num, denom);
            prob += realMod(num, denom, MOD);
            num = 1;
            denom = m;
            // prob *= s1[i]-1 / m % MOD;

        }
        if(s1[i] == 0 || s2[i] == 0){
            weird = 1;
        }
    }
    if(!weird){
        cout << 0 << endl;
    }
    else{
        // cout << num << " " << denom << endl;
        cout << prob << endl;
    }


}