24 lines
528 B
Python
24 lines
528 B
Python
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def problem_p02878(input_data):
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N, A, B = list(map(int, input_data.split()))
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M = 998244353
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P = N + 1
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f = 1
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F = [1] * P
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I = [1] * P
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z = 0
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R = range
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for n in R(1, P):
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F[n] = f = f * n % M
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I[N] = i = pow(f, M - 2, M)
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for n in R(N, 1, -1):
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I[n - 1] = i = i * n % M
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for k in R(min(A + 1, N - B) if N - B - A else A + 1):
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Q = N - B - k - 1
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z = (z + (B - k) * F[B + k - 1] * I[B] * I[k] * F[Q + A - k] * I[Q] * I[A - k]) % M
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return z if B else 1
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