A grasshopper starts at $\displaystyle 0 $ is to jump right $\displaystyle (a_1, \dots, a_n) $ in any order where each $\displaystyle a_i >0 $ and are integers. Let $\displaystyle M $ be a set of $\displaystyle n-1 $ numbers not containing $\displaystyle s = a_1 + \cdots + a_n $. Prove that the order can be chosen in such a way so that the grasshopper never lands on any point in $\displaystyle M $.