Problems
Parallelepiped#1
Very easy · Math
Grandchildren#2
Very easy · Math
Colorful Balls#3
Easy · Brute force · Combinatorics
Colorful String#4
Easy · Combinatorics · Greedy algorithms
Painting stones#5
Medium · Greedy algorithms · Math · Sorting
Pairwise Product#6
Medium · Prefix Sums · Math · Combinatorics
Sashko-Array Constructor#7
Medium · Prime factorization · Greedy algorithms
Sets#8
Medium · Combinatorics · Number theory · Binary Search
Pies#9
Very easy · Math
Arithmetic Mean#10
Very easy · Math
Cossack Vus and Friend at CP Olympiad#11
Easy · Implementation
Add and Minimize#12
Medium · Greedy algorithms · Sorting
Magic Knights#13
Medium · Combinatorics · Math
Trivial? Solve It!#14
Medium · Number theory · Math · Prefix Sums
Rook#15
Very easy · Math
Coordinates#16
Very easy · Math
Sleepy Sasha is Trouble at the University#17
Very easy · Math
Bohdan against "tails"#18
Easy · Hashing
Pasha is also against "tails"?#19
Easy · Sorting · Math
Anton buys a piglet#20
Hard · Greedy algorithms · Binary Search · Constructive Algorithms · Number theory