#include<fstream>

using namespace std;

const char InFile[]="colorare3.in";
const char OutFile[]="colorare3.out";

const int MaxN=100005;
const int MOD=1000000007;

ifstream fin(InFile);
ofstream fout(OutFile);

int n,x,y,k,grad[MaxN];

long long rez;

int main()
{
    fin>>n>>k;
    for(register int i=1;i<n;++i)
	{
        fin>>x>>y;
		++grad[x];
		++grad[y];
	}

    rez=k;
    for(register int i=1;i<=n;++i)
	{
        for(register int j=1;j<grad[i];++j)
		{
            rez=(rez*(k-j))%MOD;
		}
	}

    fout<<rez;
	return 0;
}