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"""
Problem:
Each new term in the Fibonacci sequence is generated by adding the previous two
terms. By starting with 1 and 2, the first 10 terms will be:
1,2,3,5,8,13,21,34,55,89,..
By considering the terms in the Fibonacci sequence whose values do not exceed
n, find the sum of the even-valued terms. e.g. for n=10, we have {2,8}, sum is
10.
"""
def solution(n):
"""Returns the sum of all fibonacci sequence even elements that are lower
or equals to n.
>>> solution(10)
10
>>> solution(15)
10
>>> solution(2)
2
>>> solution(1)
0
>>> solution(34)
44
"""
a = [0, 1]
i = 0
while a[i] <= n:
a.append(a[i] + a[i + 1])
if a[i + 2] > n:
break
i += 1
sum = 0
for j in range(len(a) - 1):
if a[j] % 2 == 0:
sum += a[j]
return sum
if __name__ == "__main__":
print(solution(int(input().strip())))