I had a quick guess, is No.1. * R6 S9 W! S, f6 R! s2 qBecause what ever he or she taken, the next person will take what ever had taken with +1 or -1 to ensure they havn't got the same number. at the end, no1 will had the most likely middle number and without a same number. of coz he will need to pick a number from 3 to 19.