int substr_equal(const char * a, const char * b, int size) {
    for (; size > 0; --size) {
	if (*a != *b)
	    return 0;
	++a;
	++b;
    }
    return 1;
}

int contains_double(const char * s) {
    int slen;
    for(slen = 0; s[slen] != 0; ++slen);

    for (int i = 0; s[i] != 0; ++i) {
	if (s[i] == '-') {
	    int l = i - 1;
	    if (l > slen - i)
		l = slen - i;
	    for (; l > 0; --l)
		if (substr_equal(s + i - l, s + i + 1, l))
		    return 1;
	}
    }
    return 0;
}