program nunta;
type numar=array[0..500] of longint;

var f, g:text;
    i, n, t, k, ii:longint;
    z, vg, a, b, c:numar;

function suma(x,y:numar):numar;
  begin
    z:=vg;
    t:=0;
    for ii:=1 to y[0] do
      begin
        k:=t+x[ii]+y[ii];
        z[ii]:=k mod 10;
        t:=k div 10;
      end;
    z[0]:=y[0];
    if t>0 then
      begin
        z[0]:=z[0]+1;
        z[z[0]]:=t;
      end;
    suma:=z;
  end;

  begin
    assign(f,'nunta.in'); reset(f);
    assign(g,'nunta.out'); rewrite(g);
    read(f,n);
    a[0]:=1;
    a[1]:=1;
    b[0]:=1;
    b[1]:=2;
    i:=3;
    while i<=n do
      begin
        c:=suma(a,b);
        a:=b;
        b:=c;
        i:=i+1;
      end;
    if n=1 then
      c:=a;
    if n=2 then
      c:=b;
    for i:=c[0] downto 1 do
      write(g,c[i]);
    writeln(g);
    close(f);
    close(g);
  end.