
Sum of Integers

Calculate sum of integers from 1 to given N
(including).
Input: Integer (int).
Output: Integer (int).
Examples:
assert sum_upto_n(1) == 1 assert sum_upto_n(2) == 3 assert sum_upto_n(3) == 6 assert sum_upto_n(4) == 10
How it’s used: this function can be used in a variety of mathematical and algorithmic contexts, such as in calculating the nth triangular number, determining the cost for certain operations in algorithms, etc.
Precondition:
- 1 ≤ N ≤ 900.