var n,i,a,b,c:longint;
f,g:text;
begin
assign(f,'nunta.in');reset(f);
assign(g,'nunta.out');rewrite(g);
read(f,n);
a:=1;
b:=1;
for i:=2 to n do begin
c:=a+b;
a:=b;
b:=c;
end;
write(g,c);
close(f);
close(g);
end.]