Mountains

There are $N$ mountains, each having a height $H_i$ $(1\leq i\leq N)$. Bob is standing on the first mountain. He wishes to move to the $N^{th}$ mountain. Bob can move from the $i^{th}$ mountain to the $j^{th}$ mountain if and only if $|H_i-H_j|\leq K$, where $K$ is an integer. Your task is to determine if he can reach the $N^{th}$ mountain. NOTE: the distance between the mountains doesn't ma