#include<stdio.h>

#define mod %1000000007
FILE*f=fopen("colorare3.in","r");
FILE*g=fopen("colorare3.out","w");

int n,k,v[100100],x,y,i,j,nr;


int main () {
	
	fscanf(f,"%d %d",&n,&k);
	
	for ( i = 1 ; i < n ; ++i ){
		fscanf(f,"%d %d",&x,&y);
		
		++v[x]; ++v[y];
		
	}
	
	nr = k ; 
	
	for ( i = 1 ; i <= n ; ++i ){
		
		for ( j = 1 ; j < v[i] ; ++j ){
			
			nr = (nr * ( k - j ) ) mod ;
			
		}
		
		
	}
	
	fprintf(g,"%d\n",nr) ; 
	
	fclose(f);
	fclose(g);
	return 0;
}