MOD = 10 ** 9 + 7 class CombinationCalculator: """ modを考慮したPermutation, Combinationを計算するためのクラス """ def __init__(self, size, mod): self.mod = mod self.factorial = [0] * (size + 1) self.factorial[0] = 1 for i in range(1, size + 1): self.factorial[i] = (i * self.factorial[i - 1]) % self.mod self.inv_factorial = [0] * (size + 1) self.inv_factorial[size] = pow(self.factorial[size], self.mod - 2, self.mod) for i in reversed(range(size)): self.inv_factorial[i] = ((i + 1) * self.inv_factorial[i + 1]) % self.mod def calc_combination(self, n, r): if n < 0 or n < r: return 0 if r == 0 or n == r: return 1 ans = self.inv_factorial[n - r] * self.inv_factorial[r] ans %= self.mod ans *= self.factorial[n] ans %= self.mod return ans def calc_permutation(self, n, r): if n < 0 or n < r: return 0 ans = self.inv_factorial[n - r] ans *= self.factorial[n] ans %= self.mod return ans def main(): N = int(input()) combi = CombinationCalculator(3 * N, MOD) answer = 1 l = 1 while l * 2 + N <= 2 * N: total = combi.calc_combination(N + 2 * l - 1, l) # (-N, N ) -> (l, N + l - 1) cataran = combi.calc_combination(N + 2 * l - 1, N + l) t = total - cataran t %= MOD answer += t answer %= MOD l += 1 print(answer) if __name__ == "__main__": main()