#include<fstream>
#define Mod 1000000007
#define NN 100001
 
using namespace std;
ofstream out("colorare3.out");
 
int n,v[NN];
long long ans,k;
 
int main()
{
    ifstream in("colorare3.in");
    in>>n>>k;
    for(int x,y ,i=1; i<n ;++i)
    {
        in>>x>>y;
        v[x]++;
        v[y]++;
    }
    ans=k;
    for(int i=1;i<=n;i++)
        for( int j=1;j<v[i] ;j++)
            ans= ( ans* (k-j) ) % Mod;
        out<<ans<<'\n';
        return 0;
}