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 Julia (0.5.0) (judge verdict: Accepted)

parseInt(x::String) = parse(Int, x)
parseInt(x::SubString{String}) = parse(Int, x)
parseInt(x::Char) = parse(Int, x)
parseInt(x::Float64) = trunc(Int, x)
parseFloat(x::String) = parse(Float64, x)
parseFloat(x::Int) = trunc(Float64, x)
parseFloat(x::SubString{String}) = parse(Float64, x)
parseFloat(x::Char) = parse(Float64, x)
parseMap(x::Array{SubString{String},1}) = map(parseInt, x)

function main()
    s=chomp(readline())
    i=length(s)
    ans="YES"
    while i>0
        if i<=4
            ans="NO"
            break
        elseif s[i-4:i]=="dream" || s[i-4:i]=="erase"
            i-=5
        elseif i<=5
            ans="NO"
            break
        elseif s[i-5:i]=="eraser"
            i-=6
        elseif i<=6
            ans="NO"
            break
        elseif s[i-6:i]=="dreamer"
            i-=7
        else
            ans="NO"
            break
        end
    end
    println(ans)
end
main()