SPOJ in Gyumri

   This sounds like a nice contest problem, doesn’t it? We want to give you an idea what it is like to organize a programming contest. Therefore, your task is to write a validator for the problem described above. (You may read more about validators in the validate problem.

Input

   The input contains several test cases. Each test case consists of two lines. The first line contains a single integer N (1 ≤ N ≤ 10⁶), the number of instructions that form the robot’s program. The second line contains N space-separated integers a₁ a₂ a₃ . . . a_N (1 ≤ a_i ≤ 10⁹), an encoded program for the robot, as described above.

Output

   For each test case, print exactly one line. If the given program describes a path that does not intersect itself, print “OK”. Otherwise output a single integer M (0 ≤ M < N ), the maximum number of instructions from the beginning of the program that describe a valid path. That means the path described by the program consisting of instructions a₁ a₂ a₃ . . . a_M does not intersect itself and M is maximal with this property.

Examples