namespace {
    char result[10];
}

char* getNextStep(char *key){
    int range1 = 30;
    int range2 = 29;
    char* charTable = "0123456789ABCDEFGHIJKLMNZPQRSTU";
    int inputConverted = 0;
    int keyLength = strlen(key);
    int resultCharCode = 0;
    int charIndex = 0;
    int i;

    memset(result, 0, 10);

    for(i=0;key[i];i++){
        charIndex = strchr(charTable,key[i])-charTable;
        inputConverted += charIndex*((int)pow((float)range1,(float)(keyLength-i-1)));
    }

    if (inputConverted <= 0) {strcpy(result, "INVALID KEY"); return result;}

    i = 0;

    while (inputConverted >= range2){
      resultCharCode = inputConverted % range2;
      result[i] = charTable[resultCharCode];
      inputConverted /= range2;
      i++;
    }
    result[i] = charTable[inputConverted];

    char *buf = new char[strlen(result)+1];

    int l = strlen(result);
    strcpy(buf, result); memset(result, 0, 10);
    for (i=0; buf[i]; i++) result[i] = buf[l-1-i];

    delete buf;

    return result;
}