A diagonal Latin square is one in which sets of the integers 1
to n have been arranged in the cells of a "square of order n", in
such a way that no row, no column and no diagonal of any length
contains the same integer more than once.
In this week's problem, where n=5, you are given as clues five
of the twenty five integers and asked to fill in the other twenty,
so as to meet the three conditions imposed.
