string encodeDigit(int n) {
    switch (n) {
        case 1:
            return "one";
        case 2:
            return "two";
        case 3:
            return "three";
        case 4:
            return "four";
        case 5:
            return "five";
        case 6:
            return "six";
        case 7:
            return "seven";
        case 8:
            return "eight";
        case 9:
            return "nine";
        default:
            return "";
    }
}

string encodePreTwenties(int n) {
    switch (n) {
        case 10:
            return "ten";
        case 11:
            return "eleven";
        case 12:
            return "twelve";
        case 13:
            return "thirteen";
        case 14:
            return "forteen";
        case 15:
            return "fifteen";
        case 16:
            return "sixteen";
        case 17:
            return "seventeen";
        case 18:
            return "eigteen";
        case 19:
            return "nineteen";
        default:
            return "";
    }
}

string encodeHour(int hour) {
    if (hour > 12) {
        hour = hour % 12;
    }
    
    if (hour < 10) {
        return encodeDigit(hour);
    }
    
    return encodePreTwenties(hour);
}
 
// excludes special cases like quarter
// minutes < 30
string encodeMinutes(int minutes) {
    if (minutes == 1) {
        return "one minute";    
    }
    
    if (minutes < 10) {
        return encodeDigit(minutes) + " minutes";
    }
    
    if (minutes < 20) {
        return encodePreTwenties(minutes) + " minutes";
    }
    
    if (minutes == 20) {
        return "twenty minutes";
    }
    
    return "twenty " + encodeDigit(minutes - 20) + " minutes";
}

string timeInWords(int h, int m) {
    if (m == 0) {
        return encodeHour(h) + " o' clock";  
    }
    
    if (m == 15) {
        return "quarter past " + encodeHour(h);  
    }
    
    if (m == 30) {
        return "half past " + encodeHour(h);  
    }
    
    if (m == 45) {
        return "quarter to " + encodeHour(h + 1);
    }
    
    if (m <= 30) {
        return encodeMinutes(m) + " past " + encodeHour(h);
    }
    
    // > 30 minutes
    return encodeMinutes(60 - m) +  " to " + encodeHour(h + 1);
}