IMO 1987 LL BEL9

In the set of 20 elements {1, 2, 3, 4, 5, 6, 7, 8, 9, 0, A, B, C,

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IMO 1987 LL BEL9

Origin: BEL

Problem

In the set of 20 elements {1, 2, 3, 4, 5, 6, 7, 8, 9, 0, A, B, C, D, J, K, L, U, X, Y , Z} we have made a random sequence of 28 throws. What is the probability that the sequence CUBA JULY 1987 appears in this order in the sequence already thrown?