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/**
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 * @param {number} n
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 * @return {number}
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 */
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var checkRecord = function (n) {
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  /**
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   * P(n) = A(n - 1) + P(n - 1) + L(n - 1), n ≥ 2.
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   * L(n) = A(n - 1) + P(n - 1) + A(n - 2) + P(n - 2), n ≥ 3.
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   * A(n) = A(n - 1) + A(n - 2) + A(n - 3), n ≥ 4.
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   */
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  const m = 1000000007;
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  const P = Array(n);
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  const A = Array(n);
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  const L = Array(n);
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  A[0] = 1;
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  L[0] = 1;
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  P[0] = 1;
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  A[1] = 2;
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  A[2] = 4;
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  L[1] = 3;
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  for (let i = 1; i < n; i++) {
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    P[i] = (A[i - 1] + L[i - 1] + P[i - 1]) % m;
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    if (i >= 3) A[i] = (A[i - 1] + A[i - 2] + A[i - 3]) % m;
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    if (i >= 2) L[i] = (A[i - 1] + P[i - 1] + A[i - 2] + P[i - 2]) % m;
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  }
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  return (P[n - 1] + A[n - 1] + L[n - 1]) % m;
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};