#include<cstdio>
const int N=100005;
const int MOD=1000000007;
int n,k,prod,v[N];
int main()
{
    freopen("colorare3.in","r",stdin);
    freopen("colorare3.out","w",stdout);
    scanf("%d%d",&n,&k);
    int x,y;
    for(int i=1;i<n;++i)
    {
        scanf("%d%d",&x,&y);
        v[x]++;
        v[y]++;
    }
    prod=k;
    for(int i=1;i<=n;++i)
        for(int j=1;j<v[i];++j)
            prod=((long long)prod*(k-j))%MOD;
    printf("%d",prod);
    return 0;
}