#!/usr/bin/env python

N = int(input())
slist = [int(x) for x in list(input().strip())]

for i in range(N+1):
    if (N+i-2)/2 < i:
        break
    for j in range(i, (N+i-2)//2+1):
        if slist[i:j+1] == slist[j+1:2*j-i+2]:
            print('YES')
            quit()
print('NO')