next id?

int file_proxid(FILE *arq) {
    CLEAR_ARQ;

    int last_id = -1, id = -1;
    char buffer[SIZE];

    while (fscanf(arq, "%[^','],%d,%s\n", buffer, &id, buffer) != EOF) {
        if (last_id != (id - 1) && last_id != -1) {
            id = last_id;
            break;
        }

        last_id = id;
    }

    return ++id;
}