var a,b,c,n,i:longint;
    f,g:text;
begin
assign(f,'kfib.in');reset(f);
readln(f,n);
assign(g,'kfib.out');rewrite(g);
if n<=2 then write(g,n)
else begin
a:=0; b:=1; i:=2;
repeat
i:=i+1;
c:=a+b;
a:=b;
b:=c;
until i=n;
write(g,c);
end;
close(f);  close(g);
end.