string solve(int n) {
     int i = 1;

    while (true) {
        // Convert i to binary string
        string binary = "";
        int temp = i;
        while (temp > 0) {
            binary = (temp % 2 == 0 ? '0' : '9') + binary;
            temp /= 2;
        }

        // Convert to integer and check divisibility
        long long candidate = stoll(binary);
        if (candidate % n == 0) {
            return binary;
        }

        i++;
    }
    
    return "";

}