28 lines
855 B
Python
28 lines
855 B
Python
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#!/usr/bin/env python
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import sys
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from functools import reduce
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def main() -> None:
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rep = 10000
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signal = [int(d) for d in sys.stdin.read().strip()] * rep
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offset = reduce(lambda a, b: a * 10 + b, signal[0:7])
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assert offset >= len(signal) / 2 # Sanity check
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# The trick is that the second half is only affected by itself (triangular matrix):
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# For i > len(signal) / 2, new_signal[i] = sum(signal, i, len(signal))
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# Therefore, we're only interested in numbers that start at the offset
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signal = signal[offset:] # Only take the end we need
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for __ in range(100):
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for i in range(len(signal) - 1, 0, -1): # Do the sum from the end
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signal[i - 1] += signal[i]
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signal[i - 1] = signal[i - 1] % 10
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print(reduce(lambda a, b: a * 10 + b, signal[:8]))
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if __name__ == "__main__":
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main()
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