16 lines
197 B
Python
16 lines
197 B
Python
import sys
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input = sys.stdin.readline
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N = int(input())
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D = [0] * (N+5)
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D[0] = 0
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D[1] = 0
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D[2] = 1
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D[3] = 2
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for i in range(3, N+1):
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D[i] = ((i-1) * (D[i-2] + D[i-1]))%1000000000
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print(D[N]) |