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")