uncoupled-integer.py

def main():
    values = map(int, raw_input().split(',')) 
    return reduce(lambda x, y: x ^ y, values)


print main()

# Because ^ (XOR) returns 0 for each pair and there is only one unpaired item in the input.
# E.g.
# 1 ^ 1 = 0
# 2 ^ 2 = 0
# 1 ^ 1 ^ 2 ^ 2 = 0
# 1 ^ 1 ^ 2 = 2
# 1 ^ 2 ^ 1 = 2
# Pairs rule each other out.