var a,b,f3 : array[0..10000] of integer;
    i,t,n,k : longint;
    f,g : text;
begin
assign(f,'nunta.in');reset(f);
assign(g,'nunta.out');rewrite(g);
readln(f,n);
a[0]:=1;a[1]:=1;
b[0]:=1;b[1]:=1;
if (n<=2) then
begin
  writeln(g,'1');close(g);
  halt;
end
else
Begin
  for k:=3 to n+1 do
  begin
    t:=0; i:=1;
    while (i<=a[0])or(i<=b[0])or(t<>0)do
    begin
      t:=t div 10;
      t:=t+a[i]+b[i];
      a[i]:=t mod 10;
      inc(i);
    end;
    dec(i);
    a[0]:=i;
    if a[i]=0 then a[0]:=i-1;
    f3:=a;a:=b;b:=f3;
  end;
  for i:=b[0] downto 1 do write(g,b[i]);
  writeln(g);
  close(g);
end;
end.