#include <stdio.h>
#include <stdlib.h>

// Node structure
struct Node {
    int data;
    struct Node* next;
};

struct Node* top = NULL; // top of stack

// Push function
void push(int x) {
    struct Node* newNode = (struct Node*)malloc(sizeof(struct Node));
    if (!newNode) {
        printf("Stack Overflow\n");
        return;
    }
    newNode->data = x;
    newNode->next = top;
    top = newNode;
    printf("%d pushed to stack\n", x);
}

// Pop function
void pop() {
    if (top == NULL) {
        printf("Stack Underflow\n");
        return;
    }
    struct Node* temp = top;
    printf("%d popped from stack\n", top->data);
    top = top->next;
    free(temp);
}

// Peek function
void peek() {
    if (top == NULL) {
        printf("Stack is empty\n");
        return;
    }
    printf("Top element is %d\n", top->data);
}

// Display stack
void display() {
    struct Node* temp = top;
    if (temp == NULL) {
        printf("Stack is empty\n");
        return;
    }
    printf("Stack elements: ");
    while (temp != NULL) {
        printf("%d ", temp->data);
        temp = temp->next;
    }
    printf("\n");
}

int main() {
    push(11);
    push(20);
    push(30);
    display();
    peek();
    pop();
    display();
    peek();
    return 0;
}