IceRuler has a sequence A = [a₁,a₂,...,a_n]. With a magic number m, he wants you to tell him the maximum element in these intervals [a₁,..a_m], [a₂,...a_m+1],...[a_n-m+1,...,a_n].

The first line is the magic number m. The second line contains n integers, where the i-th integer repersents the integer ai. Input ends with a number -1. Constraints: 1 ≤ m < n, 1 ≤ n ≤ 2000000, 0 ≤ ai ≤ 1000000000

Print one integer K in one line, represents the XOR sum of the maxmium elements in a[i]..a[i +m-1]s. K = the max number in [a1,..am] ⊕ the max number in [a2,..am+1] .......⊕ the max number in [an-m+1,..an]. ⊕ is the bit operation exclusive OR.

5
121 123 122 13 12 12 52 2 6 7 32 7 324 34 124 213 214 1412 -1

1178