var
  f:array[0..200000]of longint;
  x,i,j,ans,y:longint;

function fa(x:longint):longint;
begin
  if f[x]=x then exit(x);
  f[x]:=fa(f[x]);
  fa:=f[x];
end;

begin
  assign(input,'explosion.in'); reset(input);
  assign(output,'explosion.out'); rewrite(output);
  for i:=1 to 200000 do f[i]:=i;
  read(x);
  while x<>-1 do
  begin
    readln(y);
    inc(x);
    inc(y);
    if fa(x)=fa(y) then inc(ans)
    else begin
      i:=fa(x);
      j:=fa(y);
      f[j]:=i;
    end;
    read(x);
  end;
  writeln(ans);
  close(input);
  close(output);
end.