var
  x,y,a,b,ans,i:longint;
  fa:array[0..100000] of longint;
  function find(x:longint):longint;
  begin
    if x=fa[x] then exit(x)
      else fa[x]:=find(fa[x]);
    find:=fa[x];
  end;
begin
  assign(input,'explosion.in'); reset(input);
  assign(output,'explosion.out'); rewrite(output);
  for i:=0 to 100000 do
    fa[i]:=i;
  read(a);
  while a<>-1 do
    begin
      readln(b);
      x:=find(a);
      y:=find(b);
      if x<>y then
        fa[x]:=y
      else
        inc(ans);
      read(a);
    end;
  writeln(ans);
  close(input); close(output);
end.