1. The problem is to explain the concept of LIFO (Last In, First Out) in data structures. 2. LIFO is a principle used in stacks where the last element added (pushed) to the stack is the first one to be removed (popped). 3. The main operations are: - Push: Add an element to the top of the stack. - Pop: Remove the element from the top of the stack. 4. This means if you push elements in the order $a, b, c$, popping will remove them in the order $c, b, a$. 5. LIFO is used in many applications such as undo mechanisms in software, expression evaluation, and backtracking algorithms. 6. There is no specific formula but understanding the order of operations is key: the last item pushed is the first popped. 7. Example: - Push 1, stack is [1] - Push 2, stack is [1, 2] - Pop, removes 2, stack is [1] This explains the LIFO concept clearly.