arr = [1, 2, 3]
arr.append (4)
arr.append (5)
arr.pop ()
arr.append (6)
arr.append (7)
arr.pop ()
print (arr)
YXJyID0gWzEsIDIsIDNdCmFyci5hcHBlbmQgKDQpCmFyci5hcHBlbmQgKDUpCmFyci5wb3AgKCkKYXJyLmFwcGVuZCAoNikKYXJyLmFwcGVuZCAoNykKYXJyLnBvcCAoKQpwcmludCAoYXJyKQogICAgCiAgICA=