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 5.4.1) (judge verdict: Accepted)

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

char S[100000], s[4][10] = { "dream", "dreamer", "erase", "eraser" };

int hikaku(int n) {
	int i, j, len;

	for (i = 0; i < 4; i++) {
		len = strlen(s[i]);
		for (j = 1; j <= len; j++) {
			if (s[i][len - j] != S[n - j]) break;
		}
		if (j > len) {
			break;
		}
	}

	if (j > len) {
		return n - j + 1;
	}
	else {
		return -1;
	}
}

int main() {
	int len;

	scanf("%s", S);

	len = strlen(S);

	do {
		len = hikaku(len);
	} while (len != -1 && len != 0);

	if (len == 0) {
		printf("YES");
	}
	else {
		printf("NO");
	}

	return 0;
}