Program HOC24;
const fi='DULIEU.INP'
fo='KETQUA.OUT'
var f: text;
m,n,i: integer;
t: longint;
procedure ip;
begin
assign(f,fi);
reset(f);
read(f,m,n);
close(f);
end;
procedure out;
begin
assign(f,fo);
rewrite(f);
t:=0;
for i:=m to n do if i mod 2=1 then t:=t+i;
write(f,t);
close(f);
end;
begin
ip;
out;
end.