what does this code do

Q:
the input to the following C function is an array of n sorted positive
integers A[1..n], where S is the summation of all its terms (from 1 to n).

void choose(int A[], int n, int K)
{
for (k = 0; k < K; k++)
{
r = rand() % S + 1;
sum = 0;

for (i = 0; (i <= n) && (sum < r); i++)
sum += A[i];

print i;
}
}
A:
I do not know what this program does.

This is something like a puzzle that I do not solve. If you wrote this
code, you certainly should know what it does.

Regards,
Peter