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 Lua (5.3.2) (judge verdict: Accepted)

local s=io.read()
local daydream={"dream","dreamer","erase","eraser"}

while true do
    local flag=false
    for j=1,4 do
        local l=#s-#daydream[j]
        if s:sub(l+1)==daydream[j] then
            s=s:sub(1,l)
            flag=true
        end
    end
    if not flag then
        print("NO")
        break
    elseif s=="" then
        print("YES")
        break
    end
end