Buggy python submission (verdict: Time Limit Exceeded):
from sys import stdin
import sys
sys.setrecursionlimit(10**6)
def S(): return stdin.readline().rstrip()
a = S()
def f(t,a,l):
    if t == a:
        return True
    else:
        for i in l:
            if t+i in a[:len(t+i)]:
                if f(t+i,a,l):
                    return True
        return False

strl = ['dream','dreamer','erase','eraser']
if f('',a,strl):
    print('YES')
else:
    print('NO')

Fixed submission:
from sys import stdin
def S(): return stdin.readline().rstrip()

a = S()
strl = ['dream','dreamer','erase','eraser']
t = ''
for i in range(len(a)-1,-1,-1):
    if 7<len(t):
        print('NO')
        exit()
    else:
        t = a[i]+t
        if t in strl:
            t = ''

print('YES')

Buggy python submission (verdict: Time Limit Exceeded):
from sys import stdin
import sys
sys.setrecursionlimit(10**6)
def S(): return stdin.readline().rstrip()

a = S()
def f(t,a):
    if t == a:
        return True
    elif len(a)<len(t):
        return False
    else:
        strl = ['dream','dreamer','erase','eraser']
        for i in strl:
            if t+i in a[:len(t+i)]:
                if f(t+i,a):
                    return True
        return False

if f('',a):
    print('YES')
else:
    print('NO')

Fixed submission:
from sys import stdin
def S(): return stdin.readline().rstrip()

a = S()
strl = ['dream','dreamer','erase','eraser']
t = ''
for i in range(len(a)-1,-1,-1):
    if 7<len(t):
        print('NO')
        exit()
    else:
        t = a[i]+t
        if t in strl:
            t = ''

print('YES')

Buggy python submission (verdict: Time Limit Exceeded):
from sys import stdin
import sys
sys.setrecursionlimit(10**6)
def S(): return stdin.readline().rstrip()

a = S()
def f(t,a):
    if t == a:
        return True
    elif len(a)<len(t):
        return False
    else:
        strl = {0:'dream',1:'dreamer',2:'erase',3:'eraser'}
        for i in range(4):
            tmp = strl[i]
            if t+tmp in a[:len(t+tmp)]:
                if f(t+tmp,a):
                    return True
        return False

if f('',a):
    print('YES')
else:
    print('NO')

Fixed submission:
from sys import stdin
def S(): return stdin.readline().rstrip()

a = S()
strl = ['dream','dreamer','erase','eraser']
t = ''
for i in range(len(a)-1,-1,-1):
    if 7<len(t):
        print('NO')
        exit()
    else:
        t = a[i]+t
        if t in strl:
            t = ''

print('YES')

Buggy python submission (verdict: Runtime Error):
from sys import stdin
def S(): return stdin.readline().rstrip()

a = S()
def f(t,a):
    if t == a:
        return True
    elif len(a)<len(t):
        return False
    else:
        strl = {0:'dream',1:'dreamer',2:'erase',3:'eraser'}
        for i in range(4):
            tmp = strl[i]
            if t+tmp in a[:len(t+tmp)]:
                if f(t+tmp,a):
                    return True
        return False

if f('',a):
    print('YES')
else:
    print('NO')

Fixed submission:
from sys import stdin
def S(): return stdin.readline().rstrip()

a = S()
strl = ['dream','dreamer','erase','eraser']
t = ''
for i in range(len(a)-1,-1,-1):
    if 7<len(t):
        print('NO')
        exit()
    else:
        t = a[i]+t
        if t in strl:
            t = ''

print('YES')