/* There are seven ways to sum up positive integers to get the
* number five:
*
* 5
* 4 + 1
* 3 + 2
* 3 + 1 + 1
* 2 + 2 + 1
* 2 + 1 + 1 + 1
* 1 + 1 + 1 + 1 + 1
*
* Write a function that takes in a positive integer and returns
* a long long corresponding to the number of ways that positive
* integers can be added together to get the target number.
*
* (Technically, long long is not a valid C++ type, but all
* major compilers accept it and it will be valid in C++0x).
*/