#include <fstream>
#include <vector>
#include <bitset>
#include <queue>
#include <algorithm>
#include <ctime>
#include <utility>

using namespace std;

#define MOD 1000000007

ifstream cin("colorare3.in");
ofstream cout("colorare3.out");

const int MAXN = 100005;

long long n, k, sol, deg[MAXN];

int main()
{
    cin >> n >> k;
    for(int i = 1 ; i != n ; ++ i)
    {
        int a, b;
        cin >> a >> b;
        deg[a]++;
        deg[b]++;
    }
    sol = k;
    for(int i = 1; i <= n ; ++ i)
        for(int j = 1 ; j < deg[i] ; ++ j)
            sol = ((1LL*sol*(k-j)))%MOD;
    cout << sol << "\n";
    return 0;
}