{ "data": { "question": { "questionId": "2050", "questionFrontendId": "1922", "boundTopicId": null, "title": "Count Good Numbers", "titleSlug": "count-good-numbers", "content": "

A digit string is good if the digits (0-indexed) at even indices are even and the digits at odd indices are prime (2, 3, 5, or 7).

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Given an integer n, return the total number of good digit strings of length n. Since the answer may be large, return it modulo 109 + 7.

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A digit string is a string consisting of digits 0 through 9 that may contain leading zeros.

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Example 1:

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\nInput: n = 1\nOutput: 5\nExplanation: The good numbers of length 1 are "0", "2", "4", "6", "8".\n
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Example 2:

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\nInput: n = 4\nOutput: 400\n
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Example 3:

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\nInput: n = 50\nOutput: 564908303\n
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Constraints:

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Compiled with clang 11 using the latest C++ 17 standard.

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Most standard library headers are already included automatically for your convenience.

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OpenJDK 17 . Java 8 features such as lambda expressions and stream API can be used.

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Python 2.7.12.

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Compiled with gcc 8.2 using the gnu99 standard.

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C# 10 with .NET 6 runtime

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