#include <stdlib.h>
#include <stdio.h>
#include <time.h>
 
char rand_hex_string()
{
  //hexadecimal characters
  char hex_characters[]={'0','1','2','3','4','5','6','7','8','9','A','B','C','D','E','F'};
  return (char) hex_characters[rand()%16];
}
 
 
int main(int argc, char *argv[]) {
    srand(time(NULL));
    char busNo[7] = { '3', '7' , rand_hex_string() , rand_hex_string(), rand_hex_string(), rand_hex_string()};
 
printf("%s", busNo);
 
return 0;
}

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