Написать программу, определяющую период дроби

unsigned period_length(unsigned b)
{
  for (; b % 2 == 0; b /= 2);
  for (; b % 5 == 0; b /= 5);
 
  if (b <= 1)
    return 0;
 
  unsigned p = 1;
  for (unsigned d = 10 % b; d > 1; d = (d * 10) % b, ++p);
 
  return p;
}

#include <assert.h>
#include <stdlib.h>
#include <string.h>
#include <stdio.h>
 
char *periodic_decimal(unsigned a, unsigned b)
{
  assert(b > 0);
  size_t n_whole = snprintf(NULL, 0, "%u", a / b);
 
  unsigned reduced_b = b;
  unsigned n2 = 0, n5 = 0;
  for (; reduced_b % 2 == 0; reduced_b /= 2, ++n2);
  for (; reduced_b % 5 == 0; reduced_b /= 5, ++n5);
  size_t n_non_periodic = n2 >= n5 ? n2 : n5;
 
  size_t n_periodic = 0;
  if (reduced_b > 1)
  {
    n_periodic = 1;
    for (unsigned d = 10 % reduced_b; d > 1; d = (d * 10) % reduced_b, ++n_periodic);
  }
 
  size_t n_full = n_whole + 1 + n_non_periodic + (n_periodic > 0 ? 1 + n_periodic + 1 : 0);
  char *full = malloc(n_full + 1), *p = full;
 
  p += snprintf(p, n_full + 1, "%u.", a / b);
  a %= b;
  assert(p - full == n_whole + 1);
 
  for (; n_non_periodic > 0; --n_non_periodic)
  {
    assert(a < b);
    a *= 10;
    assert(a / b < 10);
    *p++ = '0' + a / b;
    a %= b;
  }
 
  if (n_periodic > 0)
  {
    *p++ = '(';
 
    for (; n_periodic > 0; --n_periodic)
    {
      assert(a < b);
      a *= 10;
      assert(a / b < 10);
      *p++ = '0' + a / b;
      a %= b;
    }
 
    *p++ = ')';
  }
 
  *p++ = '\0';
  assert(p - full == n_full + 1);
 
  return full;
}
 
int main(void)
{
  char *s;
  printf("%s\n", s = periodic_decimal(435, 28)); free(s);
  printf("%s\n", s = periodic_decimal(1, 24)); free(s);
  printf("%s\n", s = periodic_decimal(7, 12)); free(s);
  printf("%s\n", s = periodic_decimal(1, 50)); free(s);
  printf("%s\n", s = periodic_decimal(1, 3)); free(s);
}

  assert(reduced_b > 0);
  size_t n_periodic = 0;
  if (a % reduced_b != 0)
  {
    n_periodic = 1;
    for (unsigned d = 10 % reduced_b; d > 1; d = (d * 10) % reduced_b, ++n_periodic);
  }