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

int comp(const void* a, const void* b)
{
	return ( *(int*)a - *(int*)b );
}

int main ( void )
{
	int i,j ;
	int a[9]={1,3,2,5,8,4,0,9,0};
	int size = sizeof(a)/sizeof(*a);
	qsort( a, size, sizeof(*a), comp );
	for ( i = 1 ; i < size ; i++ ){
		if ( a[i]-a[i-1]>1 ){
			for ( j=a[i-1]+1 ; j<a[i] ; j++ ){
				printf ( "%d,", j ) ;
			}
		}
	}

	return 0 ;
}

6,7,