# Intermediate Combinatorics

**Discrete Mathematics**Level 4

A pair of numbers are formed from the digits 1,2,......9 such that all the digits are used up ,only once (i.e. each digit appears in only one of the numbers) .

Find the minimum difference possible between the two numbers of any such pair .

For example : 5126 and 74893 form such a pair with a difference of 69767.

Now , convert the answer you found to base 7 and calculate it's digit sum , this is your final answer.

Good Luck !!!

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