type nr_mare=array[0..200] of integer;
var a,b,c:nr_mare;
    n,i:longint;

procedure aduna(var a,b,c:nr_mare);
var i:longint;
begin
c[0]:=a[0];
if b[0]>c[0] then
        c[0]:=b[0];
for i:=1 to c[0] do
        c[i]:=a[i]+b[i];
for i:=1 to c[0] do
        begin
        inc(c[i+1],c[i] div 10);
        c[i]:=c[i] mod 10;
        end;
if c[c[0]+1]>0 then
        inc(c[0]);
end;

begin
assign(input,'nunta.in');reset(input);
assign(output,'nunta.out');rewrite(output);
readln(n);
if n<3 then
        begin
        writeln(n);
        close(output);
        halt;
        end;
a[0]:=1;a[1]:=1;
b[0]:=1;b[1]:=2;
for i:=3 to n do
        begin
        aduna(a,b,c);
        a:=b;
        b:=c;
        end;
for i:=b[0] downto 1 do
        write(b[i]);
writeln;
close(input);close(output);
end.