#include<stdio.h>
int main(){
    int top=-1,size=5;
    int arr[25];
    int isFull(){
        if(top==size-1){
        printf("stack is full\n");
       }
       else{
           arr[++top]=num;
       }
    }
    void push(int num){
    if(isFull()){
        return 1;
    }
    else{
        return 0;
    }
    
  }
  int isEmpty(){
        if(top==-1){
        printf("stack is empty\n");
            }
        else{
            top--;
        }
    }
    void pop(){
    if(isEmpty()){
        return -1;
    }
    else{
        arr[top];
    }
}
if(num<0){
    printf("Invalid input");
}
push(num);
pop();
return 0;
}