Program kfib;
var k:longint;
    f,g:text;

function fib(a:longint):longint;
begin
if a=0 then fib:=0 else
if a=1 then fib:=1 else
fib:=fib(a-2)+fib(a-1);
end;

begin
assign(f, 'kfib.in'); reset(f);
assign(g, 'kfib.out'); rewrite(g);
read(f,k);
writeln(g,fib(k));
close(f); close(g);
end.