1+3+5+7+...+107+109-2-4-6-8...-106-108 =(109-108)+(107-106)+\\\\\\+(3-2)+1=555+6-7+8-9+10-11+12-13+...+206-207+208=208-207+206-105+\\\\\\+14-13+12-11+10-9+8-7+6+5=111