Unsure on how to implement mod 10^9 +7

[krishna_kc]

Guide to modular arithmetic (plus tricks) [CodeChef edition] [There is no other edition]

Oh no, it’s another one of those problems, you have to calculate the answer modulo some huge annoying number like 10^9 + 7. But it’s okay! Modular arithmetic is really quite simple, once you get to know it (and, of course, practice it). Before I begin, some notation/clarifications: \% means modulo, and a \% m is equivalent to a \mod m. m is the modulus (such as 10^9 + 7), and for this post, m is always assumed to be prime. This will be important later. The given code is in C++. Most other l…

A wonderful guide to modular arithmetic