at break Vanya come class see array n kbit integer a_1 a_2 ldots a_n board an integer x call kbit integer 0 leq x leq 2k 1 of course Vanya able resist start change number write board to ensure note Vanya allow type change choose index array 1 leq leq n replace number a_i number overlinea_i we define overlinex kbit integer x kbit integer k bit differ corresponding bit x Vanya like number 0 therefore like segment l r 1 leq l leq r leq n a_l oplus a_l1 oplus ldot oplus a_r neq 0 oplus denote bitwise XOR operation determine maximum number segment like Vanya apply zero operation describe