#include <cstdio>
#include <cstring>
#include <algorithm>
#include <vector>
#define mod 1000000007
#define maxN 100002
using namespace std;
int n, i, j, k, V[maxN];
long long sol;
void write();
void read()
{
    int x, y;
    freopen("colorare3.in", "r", stdin);
    scanf("%d %d", &n, &k);
    for (i = 1; i <= n - 1; ++ i)
    {
        scanf("%d %d", &x, &y);
        ++ V[x];
        ++ V[y];
    }
}
void solve()
{
    sol = 1;
    for (i = 1; i <= n; ++ i)
    {
        for (j = 1; j < V[i]; ++ j)
            sol = (sol * (k - j)) % mod;
        if (i == 1)
            sol = (sol * k) % mod;
    }
}
void write()
{
    freopen("colorare3.out", "w", stdout);
    printf("%lld", sol);
    exit(0);
}
int main()
{
    read();
    solve();
    write();
    return 0;
}