[GAP Forum] A problem

[Bulutoglu Dursun A Civ AFIT/ENC]

Dear GAP Forum: 
In the below problem there was an error in the statement
The following is the corrected version of the problem:

Let Z_p be the finite field with p>7 elements. Let A be a subset of
Z_p^*={1,2,3,...p-1} with (p-1)/2 elements.

Let A=A_1UA_2 and the intersection between A_1 and A_2 be the empty set.
Furthermore 
A_1={y_1, y_1+1, y_1+2 ... y_1+s_1}  A_2={y_2, y_2+1, y_2+2 ... y_2+s_2}
where s_1+s_2+2=(p-1)/2

		For any non-zero constant c in Z_p let cA={c*a_1,c*a_2,
..., c*a_(p-1)/2} 
where A={a_1,a_2,...a_(p-1)/2}=A_1UA_2  

	Assume that for some nonzero c' (p-1)/2>=|c'A intersect
A|>=(p-3)/2 then

show that c' has to be +1 or -1 in Z_p.

I thank you for your attention.
Dursun.
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