For even integers i.e.,( 2,4 ) we have 3 per integer and for odd integers i.e.,( 1,3,5 ) we have 2 per integer… So the total is 2+3+2+3+2 = 12 but since 5 appears twice it is 12-1 = 11
For even integers i.e.,( 2,4 ) we have 3 per integer and for odd integers i.e.,( 1,3,5 ) we have 2 per integer… So the total is 2+3+2+3+2 = 12 but since 5 appears twice it is 12-1 = 11