Approximate the runtime of the following code fragment, in terms of n: Write your answer in a format such as "O(N^2)" or "O(N log N)" (without the quotes). int sum = 0; for (int i = 1; i <= n; i++) { for (int j = 1; j <= i; j += 2) { sum += 4; } } for (int k = -50; k <= -1; k++) { sum--; }