What does this C snippet output?

1#include <stdio.h>
2int once(void) {
3    static int v = 0;
4    static int init = 0;
5    if (!init) { v = 41; init = 1; }
6    return ++v;
7}
8int main(void) {
9    printf("%d\n", once());
10    printf("%d\n", once());
11    return 0;
12}