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 Pascal (FPC 2.6.2) (judge verdict: Accepted)

var a,b,c:ansistring;
i,j,p,l,x,y:longint;
begin
    readln(a);
    l:=length(a);
    while l>=5 do
    begin
        begin
       // writeln(a);
            b:=copy(a,1,6);
            if b='eraser'then delete(a,1,6)
            else
            begin
                b:=copy(a,1,7);
                if b='dreamer'then
                begin
                   x:=length(a);
                  //writeln(x);
                   if x>=10 then
                   begin
                       c:=copy(a,6,5);
                     //  writeln(c);
                       if c='erase'then
                       begin
                     //  writeln(c);
                         delete(a,1,5);
                       end
                       else delete(a,1,7);
                   end
                   else delete(a,1,7);
                end
                else
                begin
                    b:=copy(a,1,5);
                    if b='erase' then delete(a,1,5)
                    else
                    begin
                       b:=copy(a,1,5);
                       if (b='dream') then
                       begin
                          delete(a,1,5);
                       end
                       else
                       begin
                         writeln('NO');
                         halt;
                       end;
                   end;
                end;
            end;
        end;
        l:=length(a);
        if l=0 then
        begin
            writeln('YES');
            halt;
        end;
    end;
    writeln('NO');
end.