N = int(input())
S = input().strip()
if N==1:
    print("NO")
elif N==2:
    if S=="01" or S=="10":
        print("NO")
    else:
        print("YES")
elif N==3:
    if S=="010" or S=="101":
        print("NO")
    else:
        print("YES")
else:
    print("YES")