This problem was really really easy. I’m wondering if I missed something. But, it told me I could look up the algorithm for X(a, b, c), so I did.
Runs in about 3 seconds on pypy3.
def X(a, b, c):
return a ^ b ^ c
def solve(n):
total = 0
for k in range(1, n + 1):
if not X(k, 2*k, 3*k):
total += 1
return total
if __name__ == '__main__':
n = 1 << 30
print(solve(n))