记录编号	33247	评测结果	AAAAAAAAAA
题目名称	[USACO Nov10] 拜访奶牛	最终得分	100
用户昵称	Des.	是否通过	通过
代码语言	Pascal	运行时间	0.133 s
提交时间	2011-11-09 20:41:27	内存使用	1.78 MiB

program vacation;
uses math;
var f:array[1..50000,0..1]of longint;
    a:array[1..50000,1..2]of longint;
    q,next:array[0..100000]of longint;
    t,k,m,n,i,j,tot:longint;
procedure treedp(i,p:longint);
var t,k,j:longint;
begin
if (a[i,1]=a[i,2])and(q[a[i,1]]=p) then
  begin
    f[i,0]:=0;
    f[i,1]:=1;
    exit;
  end;
t:=a[i,1];
repeat
  if q[t]<>p then
    treedp(q[t],i);
  t:=next[t];
until t=0;
f[i,1]:=1;
t:=a[i,1];
repeat
  if q[t]<>p then
    begin
      f[i,0]:=f[i,0]+max(f[q[t],1],f[q[t],0]);
      f[i,1]:=f[i,1]+f[q[t],0];
    end;
  t:=next[t];
until t=0;
end;
begin
assign(input,'vacation.in');
reset(input);
assign(output,'vacation.out');
rewrite(output);
readln(n);
for t:=1 to n-1 do
  begin
    readln(i,j);
    if a[i,1]=0 then
      begin
        inc(tot);
        a[i,1]:=tot;
        a[i,2]:=tot;
        q[tot]:=j;
      end
    else
      begin
        inc(tot);
        next[a[i,2]]:=tot;
        a[i,2]:=tot;
        q[tot]:=j;
      end;
    if a[j,1]=0 then
      begin
        inc(tot);
        a[j,1]:=tot;
        a[j,2]:=tot;
        q[tot]:=i;
      end
    else
      begin
        inc(tot);
        next[a[j,2]]:=tot;
        a[j,2]:=tot;
        q[tot]:=i;
      end;
  end;
treedp(1,0);
writeln(max(f[1,0],f[1,1]));
close(output);
end.