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 C (GCC 9.2.1) (judge verdict: Accepted)

#include<stdio.h>
#include<string.h>

int main()
{
  char s[100001];
  int i,l;
  scanf("%s",s);
  l=strlen(s);
  i=l-1;
  while(1){
    if(i==-1){
      printf("YES");
      return 0;
    }
    else if(i>=6 && s[i]=='r' && s[i-1]=='e' && s[i-2]=='m' && s[i-3]=='a' && s[i-4]=='e' && s[i-5]=='r' && s[i-6]=='d'){
      i-=7;
    }
    else if(i>=5 && s[i]=='r' && s[i-1]=='e' && s[i-2]=='s' && s[i-3]=='a' && s[i-4]=='r' && s[i-5]=='e'){
      i-=6;
    }
    else if(i>=4 && s[i]=='m' && s[i-1]=='a' && s[i-2]=='e' && s[i-3]=='r' && s[i-4]=='d'){
      i-=5;
    }
    else if(i>=4 && s[i]=='e' && s[i-1]=='s' && s[i-2]=='a' && s[i-3]=='r' && s[i-4]=='e'){
      i-=5;
    }
    else{
      printf("NO");
      return 0;
    }
  }
}