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Roman Numerals

The Roman Numerals used seven capital letters correspond to the following values:

 Letters I V X L C D M Values 1 5 10 50 100 500 1000

To write all the numbers, you must meet the following rules:

1ª   If the right of a Roman letter is written the same or lower, the value it adds to the previous one.

Examples:    VI = 6;    XXI = 21;    LXVII = 67

2ª   The letter "I" placed before the "V" or "X", subtracts a unit to the next; the letter "X", preceding the "L" or "C", subtracts ten units to the next and the letter "C", preceding the "D" or "M", subtracts hundred units to the next.

Examples:    IV = 4;    IX = 9;    XL = 40;    XC = 90;    CD = 400;    CM = 900

3ª   The same letter can not be repeated more than three times in any number.

Examples:    XIII = 13;    XIV = 14;    XXXIII = 33;    XXXIV = 34

4ª   The letters "V", "L" and "D" can not be duplicated because there are other "X", "C" and "M" representing its value doubled.

Examples:    X (no VV) = 10 ;    C (no LL) = 100 ;    M (no DD) = 1.000

5ª   If in the middle of two letters there is another of less value, it subtracted its value to the next.

Examples:    XIX = 19;    LIV = 54;    CXXIX = 129

6ª   The value of Roman numerals is multiplied a thousand times as many horizontal lines are placed above them.