#include <stdio.h>

FILE *f,*s;

int n,k,x,y,i,j,v[100005];

int main()
{
	f=fopen("colorare3.in","r");
	s=fopen("colorare3.out","w");
	
	fscanf(f,"%d %d",&n,&k);
	
	for(i=1;i<n;i++)
	{
		fscanf(f,"%d %d",&x,&y);
		
		v[x]++;
		v[y]++;
	}		
	
	int res=1000000007;
	
	int rez=k;
	
    for(i=1;i<=n;i++)
	{	
        for(j=1;j<v[i];j++)
            rez=(rez*(k-j))%res;
	}
	
	fprintf(s,"%d",rez%res);
	
	fclose(s);
	
	return 0;
}