The Change Problem

Munna Bhaiya is selling guns to the people of Mirzapur. Each gun costs $Rs. 50$ There are $N$ people waiting in a queue to buy a gun from Munna and each of them either pays a $Rs. 50$ note, $Rs. 100$ note or a $Rs. 200$ note to him. Munna needs to give them back the balance amount if they pay with either Rs. 100 or Rs. 200 note. Initially Munna does not have any money. Given the sequence of the p