import sys
read = sys.stdin.buffer.read
readline = sys.stdin.buffer.readline
readlines = sys.stdin.buffer.readlines

N = int(readline())
S = read().rstrip().decode()

if N > 4:
    print('YES')
    exit()

answer = 'NO'
for T in ['00', '11', '0101', '1010']:
    if S.count(T):
        answer = 'YES'

print(answer)