Given a string, for every char (digit or alphabet) print the string from begin and end of every single element

built_strings

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

/**
 * Given a string, print subsequents for every chars
 * i.e D4b = ABCD01234ab
 **/
int main()
{
  char S[101];
  int len;
  int i;
  
  fgets(S, 101, stdin);
  
  len = strlen(S);
  S[len-1]= '\0';
  len--;

  char *p = S;  
  while(*p != '\0') {
    
    if(*p >= 48 && *p <= 57) {
      for(i=48; i<=*p; i++)
	printf("%c", i);
    }
    else if(*p >= 65 && *p <= 90) {
      for(i=65; i<=*p; i++)
	printf("%c", i);
    }
    else if(*p >= 97 && *p <= 122) {
      for(i=97; i <=*p ; i++)
	printf("%c", i);
    }
    else {
      printf("Value not valid\n");
      return -1;
    }
    p++;
  }
  printf("\n");
  
  return 0;
}