import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

/*
 * To change this template, choose Tools | Templates
 * and open the template in the editor.
 */

/**
 *
 * @author cteam084
 */
class Self {
    
    public static enum Dir
    {
        NORTH,WEST,SOUTH,EAST;
        
        
    }
    
    public static void main(String [] args)throws IOException
    {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));
        
        int numberOfInstruction = 0;
        int field[];
        do
        {
           String line = br.readLine();
           numberOfInstruction = Integer.parseInt(line);
           field = new int[numberOfInstruction];
           String [] ins = br.readLine().split(" ");
           
            for (int i = 0; i < ins.length; i++) {
                field[i] = Integer.parseInt(ins[i]);
            }
           List<Position> list = new ArrayList<Position>();
           
            Dir dir = Dir.NORTH;
            Position p = new Position(0,0);
            list.add(p);
            
            for (int i = 0; i < field.length; i++) {
                int moves = field[i];
                for (int j = 0; j < moves; j++) {
                    Position pos = move(dir, p);
                    list.add(pos);
                    p = pos;
                }
                if(contain(list))
                {
                    bw.write((i) +"\n");
                    break;
                }
                else
                {
                    if(i == field.length-1)
                    {
                        bw.write("OK\n");
                    }
                }
                
                dir = changeDir(dir);
            }
           
            
            
        }while(br.ready());
             
        
        bw.flush();
        
    }
    public static Dir changeDir(Dir d)
    {
        switch(d)
        {
            case NORTH:
                return Dir.EAST;
            case EAST:
                return Dir.SOUTH;
            case SOUTH:
                return Dir.WEST;
            case WEST:
                return Dir.NORTH;
        }
        return null;
    }
    public static Position move(Dir d,Position p)
    {
        switch(d)
        {
            case NORTH:
                return new Position(p.x,p.y+1);
            case EAST:
                return new Position(p.x+1, p.y);
            case SOUTH:
                return new Position(p.x, p.y-1);
            case WEST:
                return new Position(p.x-1, p.y);
        }
        
        return null;
    }
    public static boolean contain(List<Position> list)
    {
        for (int i = 0; i < list.size(); i++) {
            for (int j = 0; j < list.size(); j++) {
                if(i == j)
                    continue;
                else
                {
                    if(list.get(i).equals(list.get(j)))
                        return true;
                }
            }
        }
        return false;
    }
}

class Position
{
    public int x,y;

    public Position(int x, int y) {
        this.x = x;
        this.y = y;
    }

    @Override
    public boolean equals(Object obj) {
        Position p = (Position) obj;
        return this.x == p.x && this.y == p.y;
        
    }
    
    
    
    
}