program explosion;
const maxn=100001;
var
 x,ans,i,y:longint;
 fa:array[0..maxn] of longint;
 function sf(k:longint):longint;
 begin
  if fa[k]<>k then fa[k]:=sf(fa[k]) else exit(K);
  sf:=fa[k];
 end;

begin
 assign(input,'explosion.in'); reset(input);
 assign(output,'explosion.out'); rewrite(output);
 for i:=1 to maxn do fa[i]:=i;
 read(x);
 while x<>-1 do
  begin
   read(y);
   if sf(x)<>sf(y) then
    fa[sf(x)]:=sf(y) else
     ans:=ans+1;
   read(x);
  end;
 writeln(ans);
 close(input); close(output);
end.