def checku(a):
    c = 0
    for v in a:
        if c == 0:
            m = v
            c = 1
        else:
            c = c + (1 if m == v else -1)
    return a.count(m) == len(a) - 1

print(checku([1, 2]))
print(checku([1, 1, 2, 1, 1]))
print(checku([2, 1, 1, 1, 1]))
print(checku([1]))
print(checku([1, 2, 3]))
print(checku([1, 1, 2, 5, 1, 1]))
print(checku([1, 1, 1, 1, 1]))
print(checku([1, 1, 2, 2, 1]))