#include <vector>
#include <stdio.h>
#include <stdlib.h>
using namespace std;

struct Position
{
    long x,y;

};


char changeDir(char d)
    {
        switch(d)
        {
            case 'N':
                return 'E';
            case 'E':
                return 'S';
            case 'S':
                return 'W';
            case 'W':
                return 'N';
        }
        return ' ';
    }
Position move(char d,Position p)
    {
        Position newp;

        switch(d)
        {
            case 'N':
                newp.x = p.x;
                newp.y = p.y+1;
                break;
            case 'E':
                newp.x = p.x+1;
                newp.y = p.y;
                break;
            case 'S':
                newp.x = p.x;
                newp.y = p.y-1;
                break;
            case 'W':
                newp.x = p.x-1;
                newp.y = p.y;
                break;
        }

        return newp;
    }

bool contain(std::vector<Position> &list)
    {
        for (unsigned long i = 0; i < list.size(); i++) {
            for (unsigned long j = 0; j < list.size(); j++) {
                if(i == j)
                    continue;
                else
                {
                    Position tmp1 = list[i];
                    Position tmp2 = list[j];

                    if(tmp1.x == tmp2.x && tmp1.y == tmp2.y)
                        return true;

                }
            }
        }
        return false;
    }

int main()
{

        long numberOfInstruction = 0;


        do
        {
            if(scanf("%li",&numberOfInstruction) != 1)
                break;

          long *field = new long[numberOfInstruction];

            for (long i = 0; i < numberOfInstruction; i++) {
                scanf("%li",&field[i]);
            }
           std::vector<Position> list;
            char dir = 'N';
            Position p;
            p.x = 0;
            p.y = 0;

            list.push_back(p);

            for (long i = 0; i < numberOfInstruction; i++) {
                long moves = field[i];
                for (long j = 0; j < moves; j++) {
                    Position pos = move(dir, p);
                    list.push_back(pos);
                    p = pos;
                }
                if(contain(list))
                {
                    printf("%li\n",i);
                    break;
                }
                else
                {
                    if(i == numberOfInstruction-1)
                    {
                        printf("OK\n");
                    }
                }

                dir = changeDir(dir);
            }

        }while(true);







    return 0;
}