#include <cstdio>
#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
using namespace std;


int program[5];
int programIndex = 0;
bool rising;
bool solutionFound = false;
bool forceMaximum = false;
bool forceMaximumInt = 0;

int history(int now, int back)
{
   int a = now - back;
   if (a < 0)
   {
    a += 5;
   }
   return program[a];
}
void addToProgram(int novy)
{
  program[programIndex] = novy;
  programIndex++;
  if (programIndex == 5)
  {
    programIndex = 0;
  }
}
int main()
{
  int prgLength;
  while (scanf("%d", &prgLength) == 1)
  {
    solutionFound = false;
    rising = false;
    programIndex = 0;
    if (prgLength < 4) { 
      int throwAway;
      printf("OK\n");
      for (int i = 0; i <prgLength; i++) { scanf("%d", &throwAway); }
      continue;
    }
    scanf("%d %d %d %d", &program[0], &program[1], &program[2], &program[3]);
    programIndex = 4; 
    forceMaximum = false;
    if (program[2] <= program[0])
    {
      rising = false;
      if (program[3] >= program[1])
      {
        printf("3\n");
        int throwAway;
        for (int i = 4; i < prgLength; i++) { scanf("%d", &throwAway); }
        continue;
      }
    }
    else
    {
      rising = true;
      if (program[3] < program[1])
      {
       rising = false;
      }
      else if (program[3] == program[1])
      {
        rising = false;
        forceMaximum = true;
        forceMaximumInt = program[2] - program[0];
	  }
	}
	
	
	// main progress
	programIndex = 4;
	for (int fullIndex = 4; fullIndex < prgLength; fullIndex++)
	{
      int novy;
	  scanf("%d", &novy);
	  if (forceMaximum)
	  {
	    forceMaximum = false;
	    if (novy >= forceMaximumInt)
	    {
	     printf("%d\n", fullIndex);
	     solutionFound = true;
	     continue;
	    }
	  }
	  if (solutionFound)
	  {
	    continue;
	  }
	  if (rising)
	  {
	  
	    if (novy > history(programIndex, 2))
	    {
	   // printf("WAS HERE %d %d %d\n", fullIndex, novy, history(programIndex, 2));
	      addToProgram(novy);
	    }
	    else
	    {
	      rising = false;
	     // printf("DEBUG: FALL AT %d\n", fullIndex);
	      int difference = history(programIndex, 2) - history(programIndex, 4);
	      if (novy < difference)
	      {
	        rising = false;
	      }
	      else
	      {
	      	 int nahled;
	      	 bool hasNext = (fullIndex + 1 < prgLength);
	      	 if (!hasNext)
	      	 {
	     // 	   printf("DEBUG: HAS NO NEXT: fullindex %d\n", fullIndex);
	      	   solutionFound = true;
	      	   printf("OK\n");
	      	   break;
	      	 }
	      	 scanf("%d", &nahled);
	      	 int barrier = history(programIndex, 1) - history(programIndex, 3);
	      	 // int barrier = history(programIndex, 4);
	      	 addToProgram(novy);
	      	 addToProgram(nahled);
	      	 fullIndex++;
	      	 if (nahled < barrier)
	      	 {
	      	   rising = false;
	      	 }
	      	 else
	      	 {
		  	   printf("%d\n", fullIndex);
		  	   solutionFound = true;
		  	   continue;
	      	 }
		  }
	    }
	  }
	  else
	  {
	    if (novy >= history(programIndex, 2))
	    {
	      printf("%d\n", fullIndex); 
	      solutionFound = true;
	      continue;
	    }
	    else
	    {
	      addToProgram(novy);
	    }
	  }
	}
	if (!solutionFound)
	{
	 printf("OK\n");
	}	    
  }
}