IN C++

7. Find the sum 1 + 2 ... + n for a given positive integer n.

15. A prime number is an integer n > 1 whose only positive divisors are 1 and n itself. Write a boolean-valued function that determines whether an integer is a prime number.

ProgrammingProblems7&15(page195), but write one program that calls both functions, given an input( using cin).