Friends please help me how can I perform (x^y - 1)%n

Question

Where x, y, n are very large numbers .
I have used modular exponentiation , but it shows me wrong answer !
Plz give me a correct code !

Answer 1

If the number is larger than the data value can hold then you get an overflow and an incorrect result. If you’re using java try using long as your data type.

Answer 2

how to implement (x^y -1)%n .