N = int(input())
S = input()

ans = ''
if N == 1:
    ans = 'NO'
elif N == 2:
    if S == '00' or S == '11':
        ans = 'YES'
    else:
        ans = 'NO'
elif N == 3:
    if S[0] == S[1] or S[1] == S[2]:
        ans = 'YES'
    else:
        ans = 'NO'
else:
    ans = 'YES'
print(ans)