**From New Scientist #2526, 19th November 2005**

Your task this week is to put one of the letters I, V or X into each of the 21 squares in the ladder so that each row and column is a valid Roman numeral. All the numbers in the rows except one must be odd, and in only one case is a number in a row the same as a number in a column. If a letter appears in one row, it must appear in all rows above it.

What, from top to bottom, are the six numbers in the rows, expressed in the usual decimal form?

[enigma1367]

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int2roman()function in theenigma.pylibrary. This recursive Python program solves the puzzle in 48ms.Solution:The numbers in the ladder are 37, 39, 13, 3, 2 and 1.