var i,k,d,e,s:integer;
begin
k:=0;
for i:= 10 to 99 do
if i mod 2 = 1 then
d:=i div 10;
e:=i mod 10;
s:=d+e;
if ((s mod 3) = 0) then
k:=k+1;
end;
writeln(k);
end.
