nazar student scientific lyceum Kingdom Kremland know outstanding mathematical ability today math teacher give difficult taskconsider infinite set number the set consist odd positive number 1 3 5 7 ldot second set consist positive number 2 4 6 8 ldot at stage teacher write number endless blackboard set second stage number second set stage number set fourth number second set in word stage start second write time number previous change set number write the write number 1 2 4 3 5 7 9 6 8 10 Lets number number write start onethe task find sum number number l r give integer l r the answer big need find remainder division 1000000007 1097nazar think problem long time do not come solution help solve problem