Problem:
Score : 300 points

Problem Statement

You are given a string S consisting of lowercase English letters.
Another string T is initially empty.
Determine whether it is possible to obtain S = T by performing the following operation an arbitrary number of times:

Append one of the following at the end of T: dream, dreamer, erase and eraser.

Constraints

1≦|S|≦10^5

S consists of lowercase English letters.

Input

The input is given from Standard Input in the following format:

S

Output

If it is possible to obtain S = T, print YES. Otherwise, print NO.

Sample Input 1

erasedream

Sample Output 1

YES

Append erase and dream at the end of T in this order, to obtain S = T.

Sample Input 2

dreameraser

Sample Output 2

YES

Append dream and eraser at the end of T in this order, to obtain S = T.

Sample Input 3

dreamerer

Sample Output 3

NO

Solution in Fortran (GNU Fortran 9.2.1) (judge verdict: Wrong Answer)

implicit none
character(10**5+5) s,s_rev
character(5):: a
character(5):: b
character(6):: c
character(7):: d
integer:: s_len,i,count
 
a='maerd'
b='esare'
c='resare'
d='remaerd'
s_rev=''
 
read(*,*) s
s_len=len_trim(s)
 
do i=1,s_len
s_rev(s_len+1-i:s_len+1-i)=s(i:i)
end do
 
count=0
do while (count<=s_len)
if(index(s_rev,a)==1)then
count=count+len(a)
s_rev=s_rev(len(a)+1:)
 
else if(index(s_rev,b)==1)then
count=count+len(b)
s_rev=s_rev(len(b)+1:)
 
else if(index(s_rev,c)==1)then
count=count+len(c)
s_rev=s_rev(len(c)+1:)
 
else if(index(s_rev,d)==1)then
count=count+len(d)
s_rev=s_rev(len(d)+1:)
 
else
write(*,*) 'NO'
goto 100
endif
end do
 
write(*,*) 'YES'
 
100 end