s = input()
check_ls = ["a","b","c","d","e","f","g","h","i","j","k","l","m","n","o","p","q","r","s","t","u","v","w","x","y","z"]
usita_flg = 1
for i in range(len(s)):
    #print("i",i)
    if i % 2 == 0:#奇数
        if check_ls.index(s[i]) >= 0:
            #print("check_ls.index(s[i])",check_ls.index(s[i]))
            pass
        else:
            usita_flg = 0
            break
    else:#偶数
        if s[i] ==  " ":
            pass
        else:
            usita_flg = 0
            break
if usita_flg == 1:
    print("Yes")
else:
    print("No")