#include<fstream>

using namespace std;

const char iname[]="colorare3.in";
const char oname[]="colorare3.out";
const int maxn=100005;
const int mod=1000000007;
ifstream f(iname);
ofstream g(oname);

int degree[maxn],i,n,x,y,k,j;

long long rez;

int main()
{
    f>>n>>k;
    for(i=1;i<n;++i)
        f>>x>>y,++degree[x],++degree[y];

    rez=k;
    for(i=1;i<=n;++i)
        for(j=1;j<degree[i];++j)
            rez=(rez*(k-j))%mod;

    g<<rez<<"\n";
}