Program tep;
Uses crt;
Var f1,f2: text;
tong,m,n,i: integer;
Begin
Assign( f1,' C:\SONGUYEN.INP');
reset(f1);
Assign(f2,'C:\TONG.OUT');
rewrite(f2);
tong:=0;
Read( f1, m,n);
for i:=m to n do
If i mod 2 then tong:=tong+i;
Write(f2,tong);
Close(f1);
Close(f2);
End.