The Tricky Deal

One of Chef's friends offered him a deal: during $D$ days, they are going to exchange money. For each $i$ ($1 \le i \le D$), on the $i$-th day, Chef's friend would give Chef $A$ rupees, while Chef would give his friend $2^{i-1}$ rupees ($1$ rupee on day $1$, $2$ rupees on day $2$, $4$ rupees on day $3$, and so on). Chef's profit from the deal is the total number of rupees he received from his frie