Before

program fibo;

var
  s0, s1, sk: string;
  n, i: integer;

function summ(s1, s2: string): string;

var
  s, sn: string;
  a, b, c, d, k: integer;

begin

  d := 0;

  while (length(s1) > 0) do

  begin
    val(s1[length(s1)], a, k);
    delete(s1, length(s1), 1);
    val(s2[length(s2)], b, k);
    delete(s2, length(s2), 1);
    c := a + b + d;
    if (c >= 10) then
    begin
      C := c - 10;
      d := 1;
    end
    else
      d := 0;

    str(c, sn);
    s := sn + s;

  end;

  val(s2, b, k);
  c :=  b + d;
  str(c, sn);
  s := sn + s;

  summ := s;
end;

begin
  assign(input, 'input.txt');
  reset(input);
  assign(output, 'output.txt');
  rewrite(output);

  readln(n);
  i := 2;
  S0 := '0';
  S1 := '1';


  while (i <= n) do
  begin
    sk := summ(S0, S1);
    s0 := s1;
    s1 := sk;
    i := i + 1;
  end;

  if n = 0 then writeln('0')
  else if n = 1 then writeln('1')
  else while sk[1] = '0' do
    begin
      delete(sk, 1, 1);
    end;
    writeln(sk);
  close(input);
  close(output);
end.