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****.

no yes no no no yes yes no yes yes yes yes yes yes no yes yes yes yes yes yes yes yes yes yes yes no no no yes yes yes yes no no yes yes yes yes yes no yes yes no no no yes yes no yes yes no no no yes yes yes yes no yes yes yes no
/* package whatever; // don't place package name! */

import java.util.*;
import java.lang.*;
import java.io.*;

/* Name of the class has to be "Main" only if the class is public. */
public class Main
{
	public static void main (String[] args) throws java.lang.Exception
	{
		Scanner sc = new Scanner(System.in);
		sc.nextInt();
		char[] p = sc.next().toCharArray();
		int[] dists = new int[101];
		boolean works = false;
		for(int i = 0; i < p.length; i++){
			if(p[i] == '*'){
				for(int j = i+1; j < p.length; j++){
					if(p[j] == '*'){
						int curCounter = 1;
						int jump = j - i;
						for(int k = j+jump; k < p.length; k+=jump){
							if(p[k] == '*'){
								curCounter++;
							} else {
								break;
							}
							if(curCounter > 3){
								works = true;
							}
						}
					}
				}
			}
		}
		if(works){
			System.out.println("yes");
		} else {
			System.out.println("no");
		}
	}
}