private:

int size = 20, topi = -1;

int *s = (int*)malloc(sizeof(int)*size);

void sizeDoubler(){

int *temp = (int*)malloc(sizeof(int)*size*2);

for(int i = 0; i < size; i++) temp[i] = s[i];

int *temp2 = s;

s = temp;

free(temp2);

size*=2;

}

public:

int pop(){

if(topi < 0){

cout << "Stack is Empty" << endl;

}

else{

return s[topi--];

}

}

void push(int d){

while(size <= topi) sizeDoubler();

s[++topi] = d;

}

bool isEmpty(){

if(topi <= -1) return 1;

return 0;

}

int top(){

return s[topi];

}

stk *s1 = new stk();

s1->push(5);

s1->push(50);

s1->push(500);

s1->push(5000);

cout << s1->top() << endl;

for(int i = 0; i < 4; i++) cout << s1->pop() << " " ;

cout << endl << s1->isEmpty();

}