type vec=record
        a:array of longint;
        end;


var     v:array[1..100000]of vec;
        l,u,q:array[1..100000]of 1..100000;
        n,k,a,b,x,y,i,j,o,d,ll:longint;
        h:qword;
        ok:boolean;

function p(c,l:longint):qword;
var     i:longint;
begin
        p:=1;
        for i:=1 to l do
        begin
        p:=(p*c) mod 1000000007;
        dec(c);
        end;

end;

begin

assign(input,'colorare3.in');
assign(output,'colorare3.out');

reset(input);
rewrite(output);
readln(n,k);

for i:=1 to n-1 do
begin
        read(x,y);
        inc(l[x]);

        setlength(v[x].a,l[x]+1);
        v[x].a[l[x]]:=y;
        inc(l[y]);
        setlength(v[y].a,l[y]+1);
        v[y].a[l[y]]:=x;

end;

close(input);

h:=1;
i:=1;
o:=1;
q[o]:=1;
while i<=o do
begin

        ll:=0;
        ok:=false;
        if i=2 then dec(k);
        for j:=1 to l[q[i]] do
        if u[q[i]]<>v[q[i]].a[j] then
        begin

                u[v[q[i]].a[j]]:=q[i];
                inc(ll);
                inc(o);
                q[o]:=v[q[i]].a[j];
                ok:=true;
        end;

        if ok then
        h:=h*(p(k,ll) mod 1000000007);
        i:=i+1;

end;


write(h);
close(output);



end.