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Numbers in roman numerals are written with the digits I, V, X, L, C, D, M. Their values are I = 1, V = 5, X = 10, L = 50, C = 100, D = 500, M = 1000. The value of a number in roman numerals is counted by adding the values of all digits. There is an exception to this rule where the value of the next element is greater than the value of the preceding element. IV = 5 - 1 =4, IX = 10 - 1 = 9, XL = 50 - 10 = 40, XC = 100 - 10 = 90, CD = 500 - 100 = 400, CM = 1000 - 100 =900. Examples: I = 1, II = 2, III = 3, V = 5, VI = 6, VII = 7, VIII = 8, IX = 9, X = 10, XI = 11, XII = 12, XII = 13, XIV = 14, XV = 15, XVI = 16, XVII = 17, XVIII = 18, XIX = 19, XX = 20, XXIII = 23, XXX = 30, XXXV = 35, XL = 40, XLIV = 44, L = 50, LI = 51, LX = 60, LXVIII = 68, LXX = 70, LXXII = 72, LXXX = 80, LXXXIV = 84, XC = 90, XCIX = 99, C = 100, CXX = 120, CXLI = 141, CC = 200, CCL = 250, CCXXXV = 235, CCC = 300, CCCXC = 390, CCCI = 301, CD = 400, CDLXXX = 480, CDXII = 412, D = 500, DXL = 540, DLIX = 559, DC = 600, DCXXX = 630, DCXLIV = 644, DCC = 700, DCCX = 710, DCCLXI = 761, DCCC = 800, DCCCL = 850, DCCCVI = 806, CM = 900, CMLX = 960, CMLXIII = 963, M = 1000, MDCC = 1700, MCDXXX = 1430, MCDLIV = 1454, MM = 2000, MMD = 2500, MMCDXX = 2420, MMCLII = 2152, MMM = 3000.