after S[1]=9  tail = 9
after S[2]=2  tail = 2
after S[3]=5  tail = 2 5
after S[4]=3  tail = 2 3
after S[5]=7  tail = 2 3 7
after S[6]=11  tail = 2 3 7 11
after S[7]=8  tail = 2 3 7 8
after S[8]=10  tail = 2 3 7 8 10
after S[9]=13  tail = 2 3 7 8 10 13
after S[10]=6  tail = 2 3 6 8 10 13

length = 6
subsequence = 2 3 7 8 10 13
