#include <stdio.h>

char *small (char *num)
{
    static int i=0;
    if (num[i+1] == '\0')
        return NULL;
    if (num[i] < num[i+1]){
        printf("%c, %c", num[i],num[i+1]);
        i++;
        return small(num);
    }
    return &num[i];
}

int main()
{
    char *c = "1234";
    char *p = small(c);
    if (p == NULL)
        printf("null");
    else
        printf("%c",*p);
	return 0;
}