var
a:array[1..100000]of longint;
n,m,i,s,f:longint;
begin
  readln(n);
  for i:=1 to n-2 do
  begin
    read(m);
    a[m]:=1;
  end;
  f:=0;
  for i:=1 to n do
    if a[i]=0 then
    if f=0 then
    begin
      write(i);
      f:=1;
    end
    else write(' ',i);
end.
/**************************************************************
	Problem: 2029
	User: admin
	Language: Pascal
	Result: Wrong Answer
****************************************************************/