S = 2a+d(n-1)/2 *nS = 2+1(220-1)/2*220=2+219/2 *220=24310
1+219=220
2+218=220
3+217=220
109+111=220
110+220=330
220*109+330=24310
S = 2a+d(n-1)/2 *n
S = 2+1(220-1)/2*220=2+219/2 *220=24310
1+219=220
2+218=220
3+217=220
109+111=220
110+220=330
220*109+330=24310