Me, Coding Contest, Conclusion, Div484

Problem A

#this is a very simple and typical problem about how to deal with string,  
#ut i haven't considered about the initial and end problem.  
#so yeal, in initial or end point if '00' exists， it should output also  
#'No', so i can just add '0' both in end and initial of the string and at  
#the same time has no influence on others of the string.  
#Also, we avoid the situation that len(a) == 1  
def F(a):
    a = '0' + a + '0'
    if len(a) == 1:                   #this is no need
        print('Yes')
        return

    else:    
        if a.find('11') == -1:
                
            if a.find('000') == -1:
                print('Yes')
                return
            
        print('No')
        return
n = input()
a = str(input())
F(a)