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kropki game

Factorial of n!. Formula: n! = 1 * 2 * 3 * ... * n. Examples: 0! = 1, 1! = 1, 2! = 1 * 2 = 2, 3! = 1 * 2 * 3, 4! = 1 * 2 * 3 * 4, 5! = 1 * 2 * 3 * 4 * 5, 6! = 1 * 2 * 3 * 4 * 5 * 6.