N = input()
S = raw_input()
if N == 1:
    print('NO')
    quit()
if N == 2:
    if S in set(['00', '11']):
        print('YES')
    else:
        print('NO')
    quit()
if N == 3:
    if S in set(['010', '101']):
        print('NO')
    else:
        print('YES')
    quit()
print('YES')