When to take modulo

1

I am confused in taking modulo in several questions. Generally it is %1000000007, but in some cases we take %1000000006 in between. When to take %1000000007 and %1000000006?

2

Can you give an example of where you’ve seen this?

3

https://www.codechef.com/viewsolution/19196415
line 48,71 in the above solution

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4

The reasons why it switches to module 10^9+6 are explained in the Editorial.

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5

if u calculate ab %m then simple but if u wanna calculate a^b^c %m then we have to calculate res = bc %(m-1) then calculate ares %m

6

thank you!!!

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