The int that appears an odd number of times.

[wavic]

I think '&' operator will be faster

In [1]: %time 5 % 2 == 1
CPU times: user 0 ns, sys: 0 ns, total: 0 ns
Wall time: 4.05 µs
Out[1]: True

In [2]: %time 5 & 1 == 1
CPU times: user 0 ns, sys: 0 ns, total: 0 ns
Wall time: 3.1 µs
Out[2]: True