Buggy python submission (verdict: Runtime Error):
s=input()
w=["dream","dreamer","erase","eraser",""]
while True:
    

    if s[0:5]==w[0]:
        if s[5:7]=="er": #dremaerかeraserかerase
            if s[7]=="a": #erはeraseかeraserのer
                s=s[5:]
            else:
                s=s[7:]
        else:
            s=s[5:]

    elif s[0:5]==w[2]:
        if s[5]=="r": 
            s=s[6:]
        else:
            s=s[5:]
    else:
        print("NO")
        exit()

    if len(s)<=6:
        if s in w:
            print("YES")
            exit()
        else:
            print("NO")
            exit()

    #print(s)

Fixed submission:
s=input()
w=["dream","dreamer","erase","eraser",""]
while True:
    

    if s[0:5]==w[0]:
        if s[5:7]=="er": #dremaerかeraserかerase
            if s[7]=="a": #erはeraseかeraserのer
                s=s[5:]
            else:
                s=s[7:]
        else:
            s=s[5:]

    elif s[0:5]==w[2]:
        if s[5]=="r": 
            s=s[6:]
        else:
            s=s[5:]
    else:
        print("NO")
        exit()

    if len(s)<=7:
        if s in w:
            print("YES")
            exit()
        else:
            print("NO")
            exit()
    
    #print(s)

Buggy python submission (verdict: Time Limit Exceeded):
s=input()
w=["dream","dreamer","erase","eraser"]
while True:
    if len(s)==0:
        print("YES")
        exit()
    if len(s)<=4:
        print("NO")
        exit()
    
    if s[0:5]==w[0]:
        if len(s)>=7:
            if s[5:7]=="er": #dremaerかeraserかerase
                if s[7]=="a": #erはeraseかeraserのer
                    s=s[5:]
                else:
                    s=s[7:]
        else:
            s=s[5:]

    elif s[0:5]==w[2]:
        if s[5]=="r": 
            s=s[6:]
        else:
            s=s[5:]
    else:
        print("NO")
        exit()

    if len(s)==0:
        print("YES")
        exit()
    #print(s)

Fixed submission:
s=input()
w=["dream","dreamer","erase","eraser",""]
while True:
    

    if s[0:5]==w[0]:
        if s[5:7]=="er": #dremaerかeraserかerase
            if s[7]=="a": #erはeraseかeraserのer
                s=s[5:]
            else:
                s=s[7:]
        else:
            s=s[5:]

    elif s[0:5]==w[2]:
        if s[5]=="r": 
            s=s[6:]
        else:
            s=s[5:]
    else:
        print("NO")
        exit()

    if len(s)<=7:
        if s in w:
            print("YES")
            exit()
        else:
            print("NO")
            exit()
    
    #print(s)

Buggy python submission (verdict: Runtime Error):
s=input()
w=["dream","dreamer","erase","eraser"]
while True:
    if len(s)==0:
        print("YES")
        exit()
    if len(s)<=4:
        print("NO")
        exit()
    


    if s[0:5]==w[0]:
        if s[5:7]=="er": #dremaerかeraserかerase
            if s[7]=="a": #erはeraseかeraserのer
                s=s[5:]
            else:
                s=s[7:]
        else:
            s=s[5:]

    elif s[0:5]==w[2]:
        if s[5]=="r": 
            s=s[6:]
        else:
            s=s[5:]
    else:
        print("NO")
        exit()

    if len(s)==0:
        print("YES")
        exit()
    #print(s)

Fixed submission:
s=input()
w=["dream","dreamer","erase","eraser",""]
while True:
    

    if s[0:5]==w[0]:
        if s[5:7]=="er": #dremaerかeraserかerase
            if s[7]=="a": #erはeraseかeraserのer
                s=s[5:]
            else:
                s=s[7:]
        else:
            s=s[5:]

    elif s[0:5]==w[2]:
        if s[5]=="r": 
            s=s[6:]
        else:
            s=s[5:]
    else:
        print("NO")
        exit()

    if len(s)<=7:
        if s in w:
            print("YES")
            exit()
        else:
            print("NO")
            exit()
    
    #print(s)

Buggy python submission (verdict: Runtime Error):
s=input()
w=["dream","dreamer","erase","eraser"]
while True:
    if s[0:5]==w[0]:
        if s[5:7]=="er": #dremaerかeraserかerase
            if s[7]=="a": #erはeraseかeraserのer
                s=s[5:]
            else:
                s=s[7:]
        else:
            s=s[5:]

    elif s[0:5]==w[2]:
        if s[5]=="r": 
            s=s[6:]
        else:
            s=s[5:]
    else:
        print("NO")
        exit()

    if len(s)==0:
        print("YES")
        exit()
    #print(s)

Fixed submission:
s=input()
w=["dream","dreamer","erase","eraser",""]
while True:
    

    if s[0:5]==w[0]:
        if s[5:7]=="er": #dremaerかeraserかerase
            if s[7]=="a": #erはeraseかeraserのer
                s=s[5:]
            else:
                s=s[7:]
        else:
            s=s[5:]

    elif s[0:5]==w[2]:
        if s[5]=="r": 
            s=s[6:]
        else:
            s=s[5:]
    else:
        print("NO")
        exit()

    if len(s)<=7:
        if s in w:
            print("YES")
            exit()
        else:
            print("NO")
            exit()
    
    #print(s)