def checku(a):
vc = [a[0], 1, 0, 0]
for v in a[1:]:
if v == vc[0]:
vc[1] += 1
else:
if vc[3] == 0 or v==vc[2]:
vc[2] = v
vc[3] += 1
else:
return False
if vc[1] > 1 and vc[3] > 1:
return False
return vc[1]>0 and vc[3]>0
print(checku([1, 1, 2, 1, 1]))
print(checku([2, 1, 1, 1, 1]))
print(checku([1, 1, 2, 5, 1, 1]))
print(checku([1, 1, 1, 1, 1]))
print(checku([1, 1, 2, 2, 1]))
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