program zaitz;
var n, i, f, f1, f2:qword;
    {tb:array[1..300] of qword;}
    {stri:string;}
begin
assign(input, 'kfib.in');
assign(output, 'kfib.out');
reset(input); rewrite(output);
read(n);
f1:=1;
f2:=1;
i:=0;
n:=n-2;
while i<>n do begin
i:=i+1;
f:=f1+f2;
f2:=f1; f1:=f;
end;
write(f);
{str(tb[n], stri);}
close(input); close(output);
end.