var
a, b, i, tot, c1, c2: integer;
begin
readln(a, b);
tot := 0;
for i := a to b do
begin
c1 := i div 10;
c2 := i mod 10;
if (c1 + c2) mod 3 = 0 then
inc(tot);
end;
writeln(tot);
end.

输入：7 31
输出：8