#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define f first
#define s second
#define endl '\n'
#define all(x) begin(x), end(x)
#define MOD 1000000007
int n, k;
int sz[4069];
int balls[4069];
int lft[4069], rht[4069], dir[4069];
ll perm[4069][4069];
bool done[4069][4069];
ll dp[4069][4069];
int calsz(int x) {
if (!x) return 0;
return sz[x] = calsz(lft[x]) + calsz(rht[x]) + 1 - balls[x];
}
ll fnd(int x, int carry) {
if (x == 0) return carry == 0;
if (done[x][carry]) return dp[x][carry];
done[x][carry] = true;
if (carry > sz[x]) return dp[x][carry] = 0;
if (carry == sz[x]) {
ll tmp = (fnd(lft[x], sz[lft[x]]) * fnd(rht[x], sz[rht[x]])) % MOD;
tmp = (tmp * perm[carry + balls[x]][balls[x]]) % MOD;
return dp[x][carry] = tmp;
}
if (dir[x] && balls[x] + carry >= sz[rht[x]]) {
ll tmp = (fnd(lft[x], balls[x] + carry - sz[rht[x]]) * fnd(rht[x], sz[rht[x]])) % MOD;
tmp = (tmp * perm[carry + balls[x]][balls[x]]) % MOD;
dp[x][carry] = (dp[x][carry] + tmp) % MOD;
}
if (!dir[x] && balls[x] + carry >= sz[lft[x]]) {
ll tmp = (fnd(lft[x], sz[lft[x]]) * fnd(rht[x], balls[x] + carry - sz[lft[x]])) % MOD;
tmp = (tmp * perm[carry + balls[x]][balls[x]]) % MOD;
dp[x][carry] = (dp[x][carry] + tmp) % MOD;
}
for (int i = 0; i <= balls[x]; i++) {
ll tmp;
if (dir[x]) {
if (sz[rht[x]] <= carry + i) continue;
tmp = (fnd(lft[x], balls[x] - i) * fnd(rht[x], carry + i)) % MOD;
}
else {
if (sz[lft[x]] <= carry + i) continue;
tmp = (fnd(lft[x], carry + i) * fnd(rht[x], balls[x] - i)) % MOD;
}
tmp = (tmp * perm[balls[x]][balls[x] - i]) % MOD;
tmp = (tmp * perm[carry + i][i]) % MOD;
dp[x][carry] = (dp[x][carry] + tmp) % MOD;
}
//cout<<x<<' '<<carry<<'?'<<sz[x]<<':'<<dp[x][carry]<<endl;
return dp[x][carry];
}
int main() {
ios_base::sync_with_stdio(0);
cin.tie(NULL);
cin>>n>>k;
for (int i = 0; i < 4069; i++) {
perm[i][0] = 1;
for (int j = 1; j <= i; j++) {
perm[i][j] = (perm[i-1][j-1] * i) % MOD;
}
}
for (int i = 0; i < k; i++) {
int a;
cin>>a;
balls[a]++;
}
for (int i = 1; i <= n; i++) {
cin>>lft[i]>>rht[i];
dir[rht[i]] = true;
}
calsz(1);
cout<<fnd(1, 0)<<endl;
return 0;
}
