const stack = [];

function push(element) {
    stack.push(element);
}

function pop() {
    if (isEmpty()) {
        console.log("Stack is empty.");
        return null;
    }
    return stack.pop();
}

function peek() {
    if (isEmpty()) {
        console.log("Stack is empty.");
        return null;
    }
    return stack[stack.length - 1];
}

function isEmpty() {
    return stack.length === 0;
}

function size() {
    return stack.length;
}

function printStack() {
    console.log(stack);
}

console.log("Push operations:");
push(10);
push(20);
push(30);
printStack();

console.log("\nPeek operation:");
console.log(peek());

console.log("\nPop operations:");
console.log(pop());
console.log(pop());
printStack();

console.log("\nCheck if empty:");
console.log(isEmpty());

console.log("\nStack size:");
console.log(size());