#list of atoms
atoms = ["Hydrogen , Helium , Lithium"]
#main program
choice="AtomList"
while choice!="x":
    print("-------------------")
    print("A T O M F I N D E R")
    print("-------------------\n")
    print("A:Append an atom to the list")
    print("B:Removean atom from the list")
    print("C: print the list")
    print("D:Sort the atoms in the list")
    print("X:Exit he program")
    print("/n")
    choice=input("choose an option:")
    if choice== "A":
        name=input("enter the name of an atom to add:")
        atoms.append(name)
        print(name,"has been added to the list")
    if choice== "B":
        i=input("enter the name of an atom list to delete:")
        i=int(i)
        del atoms[i]
        print(name,"has been removed to the list")
    if choice=="C":
       print(atoms) 
    if choice=="D":
        atoms.sort()
    if choice=="X":
        break