Maximum Tree Jumps

Some cooking competitions going on to be held in various cities and the Chef wants to participate in them. There are $N$ cities numbered from $1$ to $N$ and they are connected by $N-1$ roads such that every city is connected to every other city. But traveling is a bit different here. Every city $i$ is assigned a travel value, $A_i$. From a city numbered $X$, one can only travel to another city $Y$