program fibonacci;

var n  :  longint;
   
function fib( n : integer) : longint;
var fi1, fi2 : longint;
   ind		 : integer;
begin
   fi1 := 0;
   fi2 := 1;
   ind := 1;
   while ind < n do
   begin
	  fi2 := fi1+fi2;
	  fi1 := fi2-fi1;
	  ind := ind +1
   end;
   fib := fi2
end; { fib }

begin
   write('n='); readln(n);
   write('fib(',n,')='); writeln(fib(n):5);
end.