var i,n:integer;
  f:text;
function Fib(N:integer):extended;
var
  F1, F2:extended;
begin
  if N=0 then Fib:=1.0
         else if N = 1 then Fib := 1.0
    else begin
      F1:=Fib(N-1);
      F2:=Fib(N-2);
      Fib:=F1+F2;
    end;
end;

begin
assign(f,'nunta.in');reset(f);
read(f,n);
close(f);
assign(f,'nunta.out');rewrite(f);
Writeln(f,fib(n):0:0);
close(f);
end.