#include <bits/stdc++.h>

using namespace std;

const int MX = 1000000, md = 1000000007;

vector<int> G[MX];
int a[MX], f[MX], g[MX], x;

int dfs(int v, int p = -1) {
    f[v] = 1;
    g[v] = 0;
    
    int S = a[v];
    for (int u : G[v]) {
        if (u == p) continue;
        S ^= dfs(u, v);
        int fv = f[v], gv = g[v];
        f[v] = (fv * 1ll * f[u] + gv * 1ll * g[u]) % md;
        g[v] = (fv * 1ll * g[u] + gv * 1ll * f[u]) % md;
    }
    
    if (p != -1) {
        int h = (f[v] + g[v]) % md;
        if (S == x) g[v] = h;
        if (S == 0) f[v] = h;
    }
    
    return S;
}

int main() {
    // freopen("out.txt", "r", stdin);
    // freopen("rs.txt", "w", stdout);
    int n;
    ignore = scanf("%d %d", &n, &x);
    for (int i = 0; i < n; i++) ignore = scanf("%d", a + i);
    for (int i = 1, u, v; i < n; i++) {
        ignore = scanf("%d %d", &u, &v);
        u--; v--;
        G[u].emplace_back(v);
        G[v].emplace_back(u);
    }
    
    int S = dfs(0), ans = 0;
    if (S == x) ans = (ans + f[0]) % md;
    if (S == 0) ans = (ans + g[0]) % md;
    
    printf("%d\n", ans);
    
    return 0;
}