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