Write it, run it, read the output

This is a scratch drill — your code runs, nothing is graded or recorded. No test cases, no expected output, no verdict.

TASK

Complete the C++ function so it returns the sum 13 for the matrix {{4, -2, 7}, {1, 0, 3}}. Initialize one accumulator before both loops, add every visited element to it, and return it after both loops.

13