BITSG string count

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Find the number of strings of length $N$ which satisfy the following conditions: 1. The string only contains characters 'B', 'I', 'T', 'S', 'G' 2. It does not contain "BITS" as a substring. 3. The above condition stays true even after swapping two adjacent characters once. As the number of strings that satisfy the above criteria may be large, output modulo 1000000007 ($10^9 + 7$). ###In

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solution.cppC++17

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