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***************************************************************************************************
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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
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

/**
 * Created by shambala on 04.04.15.
 */
public class TaskA {
    public static void main(String[] args) throws IOException {
        new TaskA().run();
    }

    public void run() throws IOException {
        BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
        int n = Integer.parseInt(in.readLine());
        String s =in.readLine();
        for (int i = 0; i<n-3;i++) {
            for (int j = 1; i+4*j<n; j++) {
                if (s.charAt(i)=='*' && s.charAt(i+j)=='*' && s.charAt(i+2*j)=='*' && s.charAt(i+3*j)=='*' && s.charAt(i+4*j)=='*') {
                    System.out.println("yes");
                    return;
                }
            }
        }
        System.out.print("no");
    }
}
