Codeforces Round #716 (Div. 2) C. Product 1 Modulo N
Educational Codeforces Round 108 (Rated for Div. 2) D. Maximum Sum of Products
Permutation Swaps!
Large Factorial
An Increment Problem
Maximal String
Minimum Appends for Palindrome!
Little Elephant and Order
Chef and Prime Divisors
The Theatre Problem