import sequtils, strutils, algorithm, math
proc scanf(fmt: cstring){.header: "<stdio.h>", varargs.}
proc scan(): int = scanf("%lld", addr result)
when (NimMajor, NimMinor) <= (0, 18): import future else: import sugar

let S = stdin.readLine()

var i = 0
var ans = "Yes"
for s in S:
  if (i mod 2) == 1:
    if s != ' ': ans = "No"
  else:
    if('a'.ord > s.ord()) or (s.ord > 'z'.ord()): ans = "No"
  i += 1

echo ans