CAPTCHA GENERATOR USING C

#include <stdio.h>
#include <stdlib.h>
#include <time.h>

int main() {
  srand(time(NULL));
  int isNumber = 0, isLowerCase = 0, isUpperCase = 0;
  char a, b, c, d, e, f, g, h;
  char captchaResult[9];

  for (int i = 1; i <= 8; i++) {
    int angka = rand() % 3 + 1;
    char random;

    if (angka == 1) {
      if (isNumber < 4) {
        random = '0' + rand() % 10;
        isNumber++;
      } else {
        i--;
        continue;
      }
    } else if (angka == 2) {
      if (isLowerCase < 2) {
        random = 'a' + rand() % 26;
        isLowerCase++;
      } else {
        i--;
        continue;
      }
    } else if (angka == 3) {
      if (isUpperCase < 2) {
        random = 'A' + rand() % 26;
        isUpperCase++;
      } else {
        i--;
        continue;
      }
    }

    if (i == 1) a = random;
    else if (i == 2) b = random;
    else if (i == 3) c = random;
    else if (i == 4) d = random;
    else if (i == 5) e = random;
    else if (i == 6) f = random;
    else if (i == 7) g = random;
    else if (i == 8) h = random;
  }

  sprintf(captchaResult, "%c%c%c%c%c%c%c%c", a, b, c, d, e, f, g, h);
  printf("CAPTCHA: %s\n", captchaResult);

  return 0;
}