20
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 97
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 56
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 51
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 99
***************************************************************************************************
 5
****.

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 math
from collections import *
from functools import reduce,cmp_to_key
import sys
input = sys.stdin.readline
M = mod = 10**9 + 7
def factors(n):return sorted(list(set(reduce(list.__add__,([i, n//i] for i in range(1, int(n**0.5) + 1) if n % i == 0)))))
def inv_mod(n):return pow(n, mod - 2, mod)

def li():return [int(i) for i in input().rstrip('\n')]
def st():return input().rstrip('\n')
def val():return int(input())

n = val()
s = st()
for i in range(len(s)):
    if s[i] == '*':
        for j in range(i):
            try:
                if s[j] == '*' and s[i+(i-j)] == '*' and s[i + 2*(i-j)] == '*':
                    print('yes')
                    exit(0)
            except:continue
print('no')