#include<stdio.h>

#define MOD 1000000007
#define ll long long

int viz[100006],n,k;
ll sol;

int main ()
{
    int i,j,a,b;
    
    freopen("colorare3.in","r",stdin);
    freopen("colorare3.out","w",stdout);
    scanf("%d%d",&n,&k);
    for(i=1;i<n;i++)
    {
        scanf("%d%d",&a,&b);
        viz[a]++;viz[b]++;
    }

    sol=k;
    
    for(i=1;i<=n;i++)
        for(j=1;j<viz[i];j++)
            sol=(sol*(k-j))%MOD;

    printf("%lld\n",sol);
    return 0;
}