#include <cstdio>

#define NMAX 100007
#define Mod 1000000007

using namespace std;

int n, a;
long long k, Ans;
int v[NMAX];

int main(){
    freopen("colorare3.in", "r", stdin);
    freopen("colorare3.out", "w", stdout);
    scanf("%d %lld", &n, &k);
    for(int i = 1; i < n; ++i){
        scanf("%d", &a);
        ++v[a];
        scanf("%d", &a);
        ++v[a];
    }
    Ans = k;
    for(int i = 1; i <= n; ++i)
        for(int j = 1; j < v[i]; ++j)
            Ans = Ans * (k - j) % Mod;
    printf("%d\n", Ans);
    return 0;
}