uses crt;
var n:integer;
function fib(n:integer):longint;
var i,k:integer;j:longint;
begin
 i:=1;j:=0;
 for k:=1 to n do begin j:=j+i;i:=j-i;end;
 fib:=j;
end;

begin
clrscr;
repeat
write('n=');readln(n);
writeln('Fib=',fib(n));
until n<0;
end.