Magician In War

There is a magician fighting against $N$ cities. City $i$ has an army with a strength of $A_i$. Let $K$ denote the city where the magician is currently at. Initially, $K = 1$. Every second, the magician can do **exactly one** of the following: - If $K \lt N$, move to the $(K+1)$-th city and hence increase $K$ by $1$; **or** - Choose an index $i \leq K$ and set $A_i$ to $0$, hence destroying th