C++

use structs/classes to implement

Ask the user to enter a positive integer n. Calculate the sum: 1+2+3,,+n (sum of first n positive integers), also the sum of the first n squares i.e. 1+2^2+3^2+4^2++n^2, then the sum of the first n cubes i.e. 1+2^3+3^3+4^3++n^3, and finally the alternating sum: 1-2+3-4+5-6+7 +-n i.e. the odds are positive and the evens are negative. Then output the results.