Assignment: #RomanNumeral Due: X/XX/MMXVII Points: III

### Specification

Write a Java application that converts integers that are less than 4000 into Roman Numerals and Roman Numerals into integers.

Prompt the user to enter either an integer or a Roman Numeral. If an integer is entered, then print its Roman Numeral equivalent; else, print the integer equivalent of the Roman Numeral. Loop until the user enters a -1. Print error messages if integers less than 1 or greater than 3999 are entered. Print error messages if invalid Roman Numerals are entered.

Your program must have a method named rntoi() that converts a roman numeral into an integer. And it must have a method named itorn() that converts an integer to roman numeral.

```   static int rntoi(String rn);
static String itorn(int n);
```
##### Roman Numeral Notes
```   I = 1
V = 5
X = 10
L = 50
C = 100
D = 500
M = 1000
```

Note: The same roman numeral digit cannot be used four times consecutively. Examples.

```   4 is IV, not IIII
9 is IX, not VIIII
40 is XL, not XXXX
90 is XC, not LXXXX
99 is XCIX, not LXXXXVIIII
```
##### Example Output

Each output line has the format: input_value " is " converted_value

```CI is 101                  <-- input: CI
101 is CI                  <-- input: 101
MMMCCCXLVIII is 3348
3348 is MMMCCCXLVIII
XCIX is 99
99 is XCIX
MMXVII is 2017
2017 is MMXVII
CCCXIV is 314
314 is CCCXIV
MIX is 1009
1009 is MIX
LIX is 59
59 is LIX
XLII is 42
42 is XLII
VIII is 8
8 is VIII
MMCXVI is 2116
2116 is MMCXVI
XLIX is 49
49 is XLIX
L is 50
50 is L
M is 1000
1000 is M
MMMCMXCIX is 3999
3999 is MMMCMXCIX
I is 1
1 is I
MCMLVII is 1957
1957 is MCMLVII
CCV is 205
205 is CCV
MMMMCXVI is invalid input
4000 is invalid input
CSC205 is invalid input
0x205 is invalid input
-1
```