Earning A Profit

There are $N$ planets numbered $1$ to $N$. You are a space merchant who earns by selling goods on these planets. Traveling to each planet requires you to pay for the fuel. The difficulty of traveling to $i$-th planet is $D_i$. You need to plan your trip by choosing a consecutive sub segment of planets. Your earning of the trip is calculated as follows - - You earn $A$ coins for every planet