MathDB

Let

m,n \geqslant 2

be integers, let

X

be a set with

n

elements, and let

X_1,X_2,\ldots,X_m

be pairwise distinct non-empty, not necessary disjoint subset of

X

. A function

f \colon X \to \{1,2,\ldots,n+1\}

is called nice if there exists an index

k

such that \sum_{x \in X_k} f(x)>\sum_{x \in X_i} f(x) \text{for all } i \ne k. Prove that the number of nice functions is at least

n^n

C5