Can someone suggest some good problems based on modular arithmetic concepts for beginners?

I am adding some interesting problems below:

https://codeforces.com/contest/1374/problem/A

https://codeforces.com/contest/1374/problem/D

Can someone suggest some good problems based on modular arithmetic concepts for beginners?

I am adding some interesting problems below:

https://codeforces.com/contest/1374/problem/A

https://codeforces.com/contest/1374/problem/D

Hackerrank and Hackerearth’s Mathematics section might help…