37 lines
708 B
Python
37 lines
708 B
Python
import sys, os
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I = list(map(int, sys.stdin.read().strip()))
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def sum_n(a, b):
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return (b-a+1)*(a+b)//2
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I = I
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j = 0
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b = 0
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res = 0
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id = len(I)//2 # last ID
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x = I[len(I)-1]
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for i in range(len(I)//2):
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if len(I)-2*j-1 - 2*i == 0:
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res += sum_n(b, b+x-1)*i
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break
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nb = b + I[2*i]
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res += sum_n(b, nb-1)*i
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b = nb
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space = I[2*i+1]
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while space > 0:
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if x > space:
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nb = b + space
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res += sum_n(b, nb-1)*id
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x -= space
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space = 0
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else:
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nb = b + x
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res += sum_n(b, nb-1)*id
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id -= 1
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space -= x
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j += 1
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x = I[len(I)-2*j-1]
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b = nb
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print(res)
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