1 var
2 max,u,v,ans,s,i,j,k,n,m:longint;
3 p,sum:array[0..100000,0..20]of longint;
4 f,d,x:Array[0..100000]of longint;
5 procedure dou(a:longint);
6 var now,i,j,k:longint;
7 begin
8 now:=x[a];
9 if a=1 then begin if now=s then inc(ans); exit;end;
10 k:=trunc(ln(d[a])/ln(2));
11 for i:=k downto 0 do
12 begin
13 if (now+sum[a,i]<=s) then
14 begin
15 now:=now+sum[a,i];
16 a:=p[a,i];
17 end;
18 if now=s then break;
19 end;
20 if now=s then inc(ans);
21 end;
22
23 begin
24 readln(n,s);
25 for i:=1 to n do
26 read(x[i]);
27 for i:=1 to n-1 do
28 begin
29 readln(u,v);
30 f[v]:=u;
31 d[v]:=d[u]+1;
32 if d[v]>max then
33 max:=d[v];
34 end;
35 k:=trunc(ln(max)/ln(2));
36 for i:=1 to n do
37 sum[i,0]:=x[f[i]];
38 for i:=1 to n do p[i,0]:=f[i];
39 for j:=1 to k do
40 for i:=1 to n do
41 begin
42 p[i,j]:=p[p[i,j-1],j-1];
43 sum[i,j]:=sum[i,j-1]+sum[p[i,j-1],j-1];
44 end;
45 for i:=1 to n do
46 if (x[i]<=s) then
47 dou(i);
48 writeln(ans);
49 end.
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