program fibonachi2;

{$APPTYPE CONSOLE}

var a:array[1..100000] of integer;
n,i:integer;
begin
readln(n);
a[1]:=1;a[2]:=1;
for i:=3 to n do
a[i]:=a[i-1]+a[i-2];
writeln(a[n]);
readln;
end.