program sir_fibonacci;
var k,t1,t2,i,t:longint;
    f,g:text;
begin
assign (f,'kfib.in'); reset (f);
assign (g,'kfib.out'); rewrite (g);
read (f,k);
t1:=0;
t2:=1;
if (k=1) then write (g,t1)
         else if (k=2) then write (g,t2)
                       else begin for i:=2 to k do begin t:=t1+t2;
                                                   t1:=t2;
                                                   t2:=t;
                                             end;
                                  write (g,t);
                            end;
close (f);
close (g);
end.