program fibonachi0;

{$APPTYPE CONSOLE}

var
f1,f2:real;
n,f:integer;
begin
readln(n);
f1:=exp(n*ln((1+sqrt(5))/2));
f2:=(exp(n*ln(abs(1-sqrt(5))/2)));
if odd(n) then f:=round(1/sqrt(5)*(f1-f2)) else f:=round(1/sqrt(5)*(f1+f2));
writeln(f);
readln;
end.