int less_than(const char * s1, const char * s2) {
    while (*s1 == *s2 && *s1 != 0) {
	++s1;
	++s2;
    }
    return (*s1 < *s2);
}

void insertion_sort(const char * S[], unsigned int n) {
    for (unsigned int i = 1; i < n; ++i) {
	for (unsigned int j = i; j > 0 && less_than(S[j], S[j-1]); --j) {
	    const char * tmp = S[j];
	    S[j] = S[j-1];
	    S[j-1] = tmp;
	}
    }
}

void sort_strings(const char * input, char * output, unsigned int n) {
    const char * S[1000];
    const char * s = input;
    for (unsigned int i = 0; i < n; ++i) {
	S[i] = s;
	while (*s)
	    ++s;
	++s;
    }
    insertion_sort(S, n);
    char * o = output;
    for (unsigned int i = 0; i < n; ++i) {
	s = S[i];
	for (;;) {
	    *o = *s;
	    if (! *o) {
		++o;
		break;
	    }
	    ++o;
	    ++s;
	}
    }
}