var n:integer;
function fblq(n:integer):integer;
var a,b,c,i:integer;
begin
a:=1;
b:=1;
if n>2
then
for i:=3 to n do
begin
c:=a+b;
a:=b;
b:=c;
end
else c:=1;
fblq:=c;
end;
begin
readln(n);
writeln(fblq(n));
end.