9 lines
281 B
Python
9 lines
281 B
Python
if __name__ == "__main__":
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N, M = int(input()), int(input())
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X = list(map(int, input().split()))
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max_dx = max([X[i + 1] - X[i] for i in range(M - 1)], default=0)
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max_h = max_dx // 2 if max_dx % 2 == 0 else max_dx // 2 + 1
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print(max([max_h, N - X[-1], X[0]]))
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