stk=[]
def push(stk,ele):
 stk.append(ele)
 
def Pop(stk):
 if len(stk)==0:
     return "Underflow"
 else:
     pop_item=stk.pop()
     return pop_item
def display(stk):
 if len(stk)==0:
     return "Underflow"
 else:
     top=len(stk)-1
     print(stk[top],"<-top")
     for i in range(top-1,-1,-1):
         print(stk[i])
while True:
     print('''
      1. Push
      2. Pop
      3. Display
      4. Exit ''')
     ch=int(input("Enter your choice:"))
     if ch==1:
         e=int(input("Enter the value to push:"))
         push(stk,e)
     elif ch==2:
        i=Pop(stk)
        if i=='Underflow':
             print("Underflow! Stack is empty")
        else:
             print("Popped Item",i)
     elif ch==3:
        display(stk)
     elif ch==4:
        break
     else:
        print("Invalid Choice")
'''
output
      1. Push
      2. Pop
      3. Display
      4. Exit 
Enter your choice:1
Enter the value to push:2
      1. Push
      2. Pop
      3. Display
      4. Exit 
Enter your choice:1
Enter the value to push:3
      1. Push
      2. Pop
      3. Display
      4. Exit 
Enter your choice:3
3 <-top
2
      1. Push
      2. Pop
      3. Display
      4. Exit 
Enter your choice:2
Popped Item 3
      1. Push
      2. Pop
      3. Display
      4. Exit 
Enter your choice:4
'''