If the vice president dies in office and the President is still alive), how is the office filled?

The United States presidential line of succession is the order in which the vice president of the United States becomes president of the United States or assumes the presidential powers and duties, via the president's death, resignation, removal from office (via impeachment conviction) or incapacity. Officials of the United States federal government (other than the vice president) assume the powers and duties of the presidency, if the president and vice president both become incapacitated, die, resign, or are removed from office, simultaneously.

i think they would live in caves or natural tunnels