#include<set>
#include<map>
#include <unordered_map>
#include <unordered_set>
#include<list>
#include<iomanip>
#include<cmath>
#include<string>
#include<vector>
#include<queue>
#include<stack>
#include<complex>
#include<sstream>
#include<iostream>
#include<fstream>
#include<algorithm>
#include<numeric>
#include<utility>
#include<functional>
#include<stdio.h>
#include<assert.h>
#include<memory.h>
#include<bitset>
#include<math.h>
#include <strings.h>




#define f first
#define s second
#define pb push_back
#define sz(a) (int)(a).size()
#define lp(i,a,n) for(int (i)=(a);(i)<=(int)(n);(i)++)
#define lpd(i,n,a) for(int (i)=(n);(i)>=(a);--(i))
#define mp make_pair
#define clr(a,b) memset(a,b,sizeof a)
#define all(v) (v).begin(),(v).end()
#define mod 1000000007
#define eps 1e-6
#define infi 1000000002
#define infll 4000000000000000005ll
#define MX 1000000
#define X real()
#define Y imag()
#define polar(r,t) ((r)* exp(point(0,(t))))
#define length(a) hypot( (a).X , (a).Y )
#define angle(a) atan2( (a).Y , (a).X )
#define vec(a,b) ( (b) - (a) )
#define dot(a,b) (conj(a)*(b)).X
#define cross(a,b) (conj(a)*(b)).Y
#define lengthsqr(a) dot(a,a)
#define reflect(V,M) (conj((V)/(M)) * (M))
#define normalize(a)   ((a)/length(a))
#define ccw(a,b,c)   cross(vec(a,b) , vec(a,c)) > -eps
#define cosRule(a,b,c) (acos(((a)*(a)+(b)*(b)-(c)*(c))/(2*(a)*(b))))
#define cosDot(a,b) (acos(dot(a,b)/length(a)/length(b)))
#define EQ(a,b) (fabs((a) - (b)) <= eps) /* equal to */
#define NE(a,b) (fabs((a) - (b)) > eps)  /* not equal to */
#define LT(a,b) ((a) < (b) - eps)        /* less than */
#define GT(a,b) ((a) > (b) + eps)        /* greater than */
#define LE(a,b) ((a) <= (b) + eps)       /* less than or equal to */
#define GE(a,b) ((a) >= (b) - eps)       /* greater than or equal to */
#define mod1 100050001
#define mod2 100030001
#define base1 37
#define base2 31
#define que priority_queue<pair<int,int>, vector<pair<int,int>> , greater<pair<int,int> > >
#define rotate(v,t) ((v)*exp(point(0,t)))
#define rotateabout(v,t,a) (rotate(vec(a,v),t)+(a))
#define PI atan(1)*4


using namespace std;
typedef long long ll;
typedef pair<int, int> pii;
typedef pair<double,double> pdd;
typedef pair<ll, ll> pll;
typedef vector<int> vi;
typedef vector<ll> vll;
typedef vector<vi> vvi;
typedef set<int> si;
typedef map<int, int> mii;
typedef map<ll, ll> mll;
typedef unordered_map<ll, ll> umll;
typedef complex<long double> point;
//typedef pair<point, point> line;
typedef pair<double , point> Circle;



const int N = 100002;

int n,m,a[N],b[N];

ll dp[N], inv;

ll power(ll b,ll p) {
    if(!p) return 1;
    ll ret = power(b, p>>1);
    return ret*ret%mod*(p&1?b:1)%mod;
}


ll solve(int i) {


    if(i == n+1) return 0;
    if(b[i] && a[i] && b[i] > a[i]) return 0;
    if(b[i] && a[i] && a[i] > b[i]) return 1;


    if(~dp[i]) return dp[i];

    ll &ret = dp[i];


    if(!a[i] && !b[i])
        ret = (((1ll*(m-1ll)*m/2ll)%mod)  + solve(i+1)*m%mod)%mod*inv%mod*inv%mod;
    else if(!a[i])
        ret = ((m-b[i]) + solve(i+1))%mod*inv%mod;
    else if(!b[i])
        ret = ((a[i]-1) + solve(i+1))%mod*inv*mod;
    else
        ret = solve(i+1);

    return ret;
}

int main(){
    scanf("%d%d",&n,&m);
    lp(i, 1, n) scanf("%d",&a[i]);
    lp(i, 1, n) scanf("%d",&b[i]);

    inv = power(m, mod-2);
    clr(dp, -1);
    printf("%lld\n", solve(1));


    return 0;
}

/*


 7
 10
 5 7 1
 5 6 2
 7 7 2
 6 7 2
 5 5 1
 3 6 2
 1 3 2
 5 6 1
 1 3 1
 6 7 1



 */
//freopen("output.txt","w",stdout);
//freopen("input.txt","r",stdin);
//ios::sync_with_stdio(0);cin.tie(0);