#the list of atoms
atoms=["hydogen","helium","lithium","beryllium","boron","carbon","nitrogen","oxygen","fluorine","neon","sodium","magnesium","aluminium","silicon","phosphorus","sulfer","chlorine","argon","potassium","calcium","scandium","titanium","vanadium","chromium","manganese","iron","cobalt","nickel","copper","zinc","gallium","germanium","arsenic","selemium","bromine","krypton","rubidium","strontium","yttrium","zirconium","niobium","molybdenem","technetium","ruthenium","rhodium","palladium","silver","cadmium","indium","tin","antimony","tellurium","iodine","xenon","cesium","barium","lanthanum","cerium","praseodymium","neodymium","promethium","samarium","europium","gadolinium","terbium","dysprosium","holmium","erbium","thulium","ytterbium","lutetium","hafnium","tantalum","tungsten","rhenium","osmium","iridium","platinum","gold","mercury","thallium","lead","bismuth","polonium","astatine","radon","francium","radium"]
#main program
choice=""
while choice !="x":
    print("**************************************")
    print("     A  T  O  M  F  I  N  D  E  R     ")
    print("**************************************")
    print("\n")
    print("A:Append an atom to the list")
    print("B: Remove an atom from the list")
    print("C: Print the list")
    print("D: Sort the list")
    print("E: the length of list")
    print("F: edit an atom")
    print("X: Exit the 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":
        name=input("enter the name of an atom to remove")
        atoms.remove(name)
        print(name,"has been removed from the list")
       
    if choice=="C":
        print(atoms)
   
    if choice=="D":
        atoms.sort()
        print(atoms)

    if choice=="E":
        print(len(atoms))
       
    if choice=="F":
        print(atoms)
        i=int(input("which atom do you want to change?"))
        atoms[i]=input("enter a new atom")
        print(atoms)