The 9 digits: 1,2,3,4,5,6,7,8,9
PAIR = 2 digits in ascending order; example 37 ; 1st digit < 2nd digit
So there are 36 PAIRs using the 9 digits:
12, 13, 14, ... , 78, 79, 89
3DN = 3 digit number, digits in ascending order; example 238 ; 1st digit < 2nd digit < 3rd digit
So there are 84 3DNs using the 9 digits:
123, 124, 125, ... , 679, 689, 789
A 3DN contains 3 PAIRs; example: 238 contains 23, 28 and 38
Your mission:
find 12 3DNs that together will contain all 36 PAIRs.