算余数

[（ヅ）]

12^{{34}^{{56}^{78}}} \text{ mod } 90

[YWY]

This number is 0 mod 9, 0 mod 2, and 1 mod 5. So it is 36 mod 90. (It is 1 mod 5 because {34}^{{56}^{78}} is 0 mod 4 and 12 is not 0 mod 5, with 5 a prime number.)