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 (gfortran v4.8.4) (judge verdict: Accepted)

implicit none
integer(8):: n,y,i,j,count,s_len
character(10**5+5)::s,s_rev
character(5)::a
character(5)::b
character(6)::c
character(7)::d
 
a="maerd"
b="esare"
c="resare"
d="remaerd"
 
s_rev=""
 
read(5,*) s
s_len=len_trim(s)
 
do i=1,s_len
    s_rev(s_len+1-i:s_len+1-i)=s(i:i)
enddo
 
!write(6,*) trim(s_rev)
 
count=1
 
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(6,*) "NO"
        goto 100
        
    endif

    
enddo
 
write(6,*) "YES"
 
100 end