#include <fstream>
#include <cstring>
using namespace std;
long long sol;
int x,y,k,i,j,fii[100001],n;
int main()
{
    ifstream fi("colorare3.in");
    ofstream fo("colorare3.out");
    fi>>n>>k;
    memset(fii,0,sizeof(fii));
    for(i=1;i<=n-1;i++)
    {
        fi>>x>>y;
        fii[x]++; fii[y]++;
    }
    sol=k;
    for(i=1;i<=n;i++)
    {
        for(j=1;j<fii[i];j++)
        sol=(sol*(k-j))%1000000007;
    }

    fo<<sol%1000000007<<"\n";
    fo.close();
    return 0;
}