OddoccurrencesInarray
//correctness 100% perfomance 25%
def solution(A):
for number in A:
if number != '-':
A[A.index(number)] = '-'
if number in A:
A[A.index(number)] = '-'
else:
return number
A= [9,3,9,3,9,7,9]
solution(A)
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