#include <cstdio>
#define DN 100001
#define REST 1000000007
int x,y,n,i,j,grad[DN];
long long sol,k;
int main()
{
	freopen("colorare3.in","r",stdin);
	freopen("colorare3.out","w",stdout);
	scanf("%d %lld",&n,&k );
	for(i=1; i<n; ++i) {
	    scanf("%d %d",&x,&y );
	    ++grad[x];
	    ++grad[y];
	}
	sol=k;
    for(i=1; i<=n;++i)
        for(j=1; j<grad[i]; ++j)
            sol=(sol*(k-j))%REST;
    printf("%lld",sol);
	return 0;
}