void generate_valid_prefix(char* output, Xoshiro256plus& rng) {

    char first_char = 'K' + (rng.next() % 2); 
    char second_char = (first_char == 'K') ? 
    BASE58[57 - (rng.next() % 10)] : BASE58[rng.next() % 5];
    output[0] = first_char;
    output[1] = second_char;
    output[2] = '\0'; 
}

static const char VALID_PREFIXES[][3] = {
    "Kw", "Kx", "Ky", "Kz", "L1", "L2", "L3", "L4", "L5"
};

static constexpr size_t NUM_PREFIXES = sizeof(VALID_PREFIXES) / sizeof(VALID_PREFIXES[0]);

void generate_valid_prefix(char* output, Xoshiro256plus& rng) {
    // Generate a random index in [0, NUM_PREFIXES - 1]
    uint64_t random_index = rng.next() % NUM_PREFIXES;

    output[0] = VALID_PREFIXES[random_index][0];
    output[1] = VALID_PREFIXES[random_index][1];
    output[2] = '\0'; // Null terminator
}