Contest starts in 30 minutes.

Codechef is literally beyond parody at this point. For anyone fortunate enough to not have taken this round, here are three problems that were considered worth putting into a "rated till 2500" round:

1. Sum of XOR of prefix maximums over all rearrangements of an array.
2. Sum of a contrived f(sequence) over all subsequences of all reversed prefixes of an array.
3. Sum of sum(arr) - min(arr) over all arrays in $$$[1, m]^n$$$

It increasingly feels like the primary strategy adopted by "problemsetters" at codechef is something like the following:

ops = {"SUM", "PRODUCT", "GCD", "MAX", "MIN", "OR_SUM", "XOR_SUM", "OR_SUM", "AND_SUM", "ALTERNATING_SUM", ...}
scopes = {"OVER_ALL_PREFIXES", "OVER_ALL_SUFFIXES", "OVER_ALL_SUBARRAYS", "OVER_ALL_SUBSEQUENCES", "OVER_ALL_POSSIBLE_ARRAYS", ...}

number_of_ops = rng(1, 5)
number_of_scopes = rng(1, 5)

used_ops = {}
while used_ops.size() < number_of_ops:
    used_ops.push_back(rng(ops))

used_scopes = {}
while used_scopes.size() < number_of_scopes:
    used_scopes.push_back(rng(scopes))

problem_statement = rng_combine(used_ops, used_scopes)

final_problem_statement = add_or_remove_a_couple_of_modifiers(problem_statement)