Valkyrie in a Venture

There are $N$ towers in Asgard on points $1$ to $N$ inclusive on the $OX$ axis. For each valid $i$, the $i$-th tower has height $H_i$. Valkyrie is standing at point $0$ at height $0$ at ground level. If she starts to fly from height $0$ she can cover a total distance of $2*D$ from point $0$. There are $K$ boxes beside her which she can use to stand at any height from $0$ to $K$ from ground. Va