while True:
    string = raw_input()
    if len(string)<3 or len(string)%2==0 or string[len(string)/2]!='&':
        print "NO"
        continue
    i = 0
    j = len(string)-1
    while i<j and string[i]>='a' and string[i]<='z' and string[i]==string[j]:
        i+=1
        j-=1
    if i<j:print "NO"
    else:print "YES"

/**************************************************************
	Problem: 2225
	User: admin
	Language: Python
	Result: Wrong Answer
****************************************************************/