function fibo(M,N,R:integer):integer;
var x:real;
begin
 if (N=1) then fibo:=0
 else if (N=2) then fibo:=1
 else begin
   x:=M*1.618;
   if N=(R+2) then fibo:=M
   else fibo:=fibo(round(x),N,R+1);
 end;
end;

var N : integer;

begin
  readln(N);
  writeln(fibo(1,N,0));
end.