it says that the question we ask is “1 i j k” where i!=j, j!=k and k!=i

but subtask 1 says that i=j=k

how?

Subtask 1 is an easier part of the problem in which you i can be equal to j and k. If you use this, then you won’t get AC for the whole program but only partial marks (for the 1st Subtask).