{ "data": { "question": { "questionId": "1461", "questionFrontendId": "1359", "boundTopicId": null, "title": "Count All Valid Pickup and Delivery Options", "titleSlug": "count-all-valid-pickup-and-delivery-options", "content": "

Given n orders, each order consist in pickup and delivery services. 

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Count all valid pickup/delivery possible sequences such that delivery(i) is always after of pickup(i). 

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Since the answer may be too large, return it modulo 10^9 + 7.

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Example 1:

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\nInput: n = 1\nOutput: 1\nExplanation: Unique order (P1, D1), Delivery 1 always is after of Pickup 1.\n
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Example 2:

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\nInput: n = 2\nOutput: 6\nExplanation: All possible orders: \n(P1,P2,D1,D2), (P1,P2,D2,D1), (P1,D1,P2,D2), (P2,P1,D1,D2), (P2,P1,D2,D1) and (P2,D2,P1,D1).\nThis is an invalid order (P1,D2,P2,D1) because Pickup 2 is after of Delivery 2.\n
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Example 3:

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\nInput: n = 3\nOutput: 90\n
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Constraints:

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