Let stack ptr be a pointer to a stack of integers. Use the functions Push, Pop, Initialize, Empty, and Full to write a function to return the value of the third element from the stack, provided the stack contains at least three integers. If not, return an error message. Leave the stack unchanged. You may declare additional variables in your function, if needed. Note that you are not required to write any of the Push, Pop, Initialize, Empty, and Full functions; assume they are available.