Buggy python submission (verdict: Time Limit Exceeded):
S = input()

from collections import deque

q = deque()
if len(S) > 5: #4文字以下ならそもそもバツ→入れない
  q.append((len(S), S))
#ここに、次にチェックする文字列を入れていく
#今回はque(fi-fo)として使うので、popleftを使う

flag = False
while(q):
  nowlen, nows = q.popleft()
  nows5 = nows[0:5]
  nowsfrom5 = nows[5:]
  if nows5 == 'dream':
    if nowlen == 5:
      flag = True
      break
    else:
      if nowlen>=10: q.append((nowlen-5, nowsfrom5))
    if nows[0:7] == 'dreamer':
      if nowlen == 7:
        flag = True
        break
      else:
        if nowlen>=12: q.append((nowlen-7, nows[7:]))
  elif nows5 == 'erase':
    if nowlen == 5:
        flag = True
        break
    else:
      if nowlen>=10: q.append((nowlen-5, nowsfrom5))
    if nows[0:6] == 'eraser':
      if nowlen == 6:
        flag = True
        break
      else: 
        if nowlen>=11: q.append((nowlen-6, nows[6:]))

print('YES' if flag else 'NO')

Fixed submission:
S = input()

from collections import deque

q = deque()
if len(S) > 5: #4文字以下ならそもそもバツ→入れない
  q.append((len(S), S))
#ここに、次にチェックする文字列を入れていく
#今回はque(fi-fo)として使うので、popleftを使う

flag = False
while(q):
  nowlen, nows = q.popleft()
  nows5 = nows[0:5]
  nowsfrom5 = nows[5:]
  if nows5 == 'dream':
    if nowlen == 5:
      flag = True
      break
    else:
      if nowlen>=10: q.append((nowlen-5, nowsfrom5))
    if nows[0:7] == 'dreamer':
      if nowlen == 7:
        flag = True
        break
      else:
        if nowlen>=12: q.append((nowlen-7, nows[7:]))
  elif nows5 == 'erase':
    if nowlen == 5:
        flag = True
        break
    else:
      if nowlen>=10: q.append((nowlen-5, nowsfrom5))
    if nows[0:6] == 'eraser':
      if nowlen == 6:
        flag = True
        break
      else: 
        if nowlen>=11: q.append((nowlen-6, nows[6:]))

print('YES' if flag else 'NO')

Buggy python submission (verdict: Time Limit Exceeded):
S = input()

from collections import deque

q = deque()
if len(S) > 5: #4文字以下ならそもそもバツ→入れない
  q.append(S)
#ここに、次にチェックする文字列を入れていく
#今回はque(fi-fo)として使うので、popleftを使う

flag = False
while(q):
  nows = q.popleft()
  nows5 = nows[0:5]
  nowsfrom5 = nows[5:]
  if nows[0:5] == 'dream':
    if nows[5:] == '':
      flag = True
      break
    else:
      if not(len(nowsfrom5)<=4): q.append(nows[5:])
    if nows[0:7] == 'dreamer':
      if nows[7:] == '':
        flag = True
        break
      else:
        if not(len(nows[7:])<=4): q.append(nows[7:])
  elif nows[0:5] == 'erase':
    if nows[5:] == '':
        flag = True
        break
    else:
      if not(len(nowsfrom5)<=4): q.append(nowsfrom5)
    if nows[0:6] == 'eraser':
      if nows[6:] == '':
        flag = True
        break
      else: 
        if not(len(nows[6:])<=4): q.append(nows[6:])

print('YES' if flag else 'NO')

Fixed submission:
S = input()

from collections import deque

q = deque()
if len(S) > 5: #4文字以下ならそもそもバツ→入れない
  q.append((len(S), S))
#ここに、次にチェックする文字列を入れていく
#今回はque(fi-fo)として使うので、popleftを使う

flag = False
while(q):
  nowlen, nows = q.popleft()
  nows5 = nows[0:5]
  nowsfrom5 = nows[5:]
  if nows5 == 'dream':
    if nowlen == 5:
      flag = True
      break
    else:
      if nowlen>=10: q.append((nowlen-5, nowsfrom5))
    if nows[0:7] == 'dreamer':
      if nowlen == 7:
        flag = True
        break
      else:
        if nowlen>=12: q.append((nowlen-7, nows[7:]))
  elif nows5 == 'erase':
    if nowlen == 5:
        flag = True
        break
    else:
      if nowlen>=10: q.append((nowlen-5, nowsfrom5))
    if nows[0:6] == 'eraser':
      if nowlen == 6:
        flag = True
        break
      else: 
        if nowlen>=11: q.append((nowlen-6, nows[6:]))

print('YES' if flag else 'NO')

Buggy python submission (verdict: Time Limit Exceeded):
S = input()

from collections import deque

q = deque()
q.append(S)
#ここに、次にチェックする文字列を入れていく
#今回はque(fi-fo)として使うので、popleftを使う

flag = False
while(q):
  nows = q.popleft()
  if len(nows) <= 4: continue
    #残りが4文字以下だと絶対違う
    #またほっとくと添字バグが起きる
  if nows[0:5] == 'dream':
    if nows[5:] == '':
      flag = True
      break
    else: q.append(nows[5:])
    if nows[0:7] == 'dreamer':
      if nows[7:] == '':
        flag = True
        break
      else: q.append(nows[7:])
  elif nows[0:5] == 'erase':
    if nows[5:] == '':
        flag = True
        break
    else: q.append(nows[5:])
    if nows[0:6] == 'eraser':
      if nows[6:] == '':
        flag = True
        break
      else: 
        q.append(nows[6:])

print('YES' if flag else 'NO')

Fixed submission:
S = input()

from collections import deque

q = deque()
if len(S) > 5: #4文字以下ならそもそもバツ→入れない
  q.append((len(S), S))
#ここに、次にチェックする文字列を入れていく
#今回はque(fi-fo)として使うので、popleftを使う

flag = False
while(q):
  nowlen, nows = q.popleft()
  nows5 = nows[0:5]
  nowsfrom5 = nows[5:]
  if nows5 == 'dream':
    if nowlen == 5:
      flag = True
      break
    else:
      if nowlen>=10: q.append((nowlen-5, nowsfrom5))
    if nows[0:7] == 'dreamer':
      if nowlen == 7:
        flag = True
        break
      else:
        if nowlen>=12: q.append((nowlen-7, nows[7:]))
  elif nows5 == 'erase':
    if nowlen == 5:
        flag = True
        break
    else:
      if nowlen>=10: q.append((nowlen-5, nowsfrom5))
    if nows[0:6] == 'eraser':
      if nowlen == 6:
        flag = True
        break
      else: 
        if nowlen>=11: q.append((nowlen-6, nows[6:]))

print('YES' if flag else 'NO')