Buggy python submission (verdict: Time Limit Exceeded):
S = input()

i = 0
while i <= len(S) - 1:
    if S[i] == "d":
        if i + 10 < len(S):
            if S[i + 10]  == "r":
                if S[i:i+11] != "dreameraser":
                    print("NO")
                    exit()
                else:
                    i += 11
        elif i + 6 < len(S):
            if S[i+6] == "r":
                if S[i:i+7] != "dreamer":
                    print("NO")
                    exit()
                else:
                    i += 7
            elif S[i:i+6] != "dream":
                print("NO")
                exit()
            else:
                i += 6
        elif S[i:i+6] != "dream":
                print("NO")
                exit()
        else:
            i += 6
    elif S[i] == "e":
        if i + 5 < len(S):
            if S[i+5] == "r":
                if S[i:i+6] != "eraser":
                    print("NO")
                    exit()
                else:
                    i += 6
            elif S[i:i+5] != "erase":
                print("NO")
                exit()
            else:
                i += 5
        elif S[i:i+5] != "erase":
                print("NO")
                exit()
        else:
            i += 5
    else:
        print("NO")
        exit()
print("YES")


Fixed submission:
T = input()

S = T[::-1]
i = 0
while i <= len(S) - 1:
    if S[i] == "r":
        if S[i:i+7] == "remaerd":
            i += 7
        elif S[i:i+6] == "resare":
            i += 6
        else:
            print("NO")
            exit()
    elif S[i] == "m":
        if S[i:i+5] == "maerd":
            i += 5
        else:
            print("NO")
            exit()
    elif S[i] == "e":
        if S[i:i+5] == "esare":
            i += 5
        else:
            print("NO")
            exit()
    else:
        print("NO")
        exit()
print("YES")

Buggy python submission (verdict: Time Limit Exceeded):
S = input()

candidate = ["dream", "dreamer", "erase", "eraser", "dreameraser"]

i = 0
while i <= len(S) - 1:
    if S[i] == "d":
        if i + 10 < len(S):
            if S[i + 10]  == "r":
                if not S[i:i+11] in candidate:
                    print("NO")
                    exit()
                else:
                    i += 11
        elif i + 6 < len(S):
            if S[i+6] == "r":
                if not S[i:i+7] in candidate:
                    print("NO")
                    exit()
                else:
                    i += 7
            elif not S[i:i+6] in candidate:
                print("NO")
                exit()
            else:
                i += 6
        elif not S[i:i+6] in candidate:
                print("NO")
                exit()
        else:
            i += 6
    elif S[i] == "e":
        if i + 5 < len(S):
            if S[i+5] == "r":
                if not S[i:i+6] in candidate:
                    print("NO")
                    exit()
                else:
                    i += 6
            elif not S[i:i+5] in candidate:
                print("NO")
                exit()
            else:
                i += 5
        elif not S[i:i+5] in candidate:
                print("NO")
                exit()
        else:
            i += 5
    else:
        print("NO")
        exit()
print("YES")


Fixed submission:
T = input()

S = T[::-1]
i = 0
while i <= len(S) - 1:
    if S[i] == "r":
        if S[i:i+7] == "remaerd":
            i += 7
        elif S[i:i+6] == "resare":
            i += 6
        else:
            print("NO")
            exit()
    elif S[i] == "m":
        if S[i:i+5] == "maerd":
            i += 5
        else:
            print("NO")
            exit()
    elif S[i] == "e":
        if S[i:i+5] == "esare":
            i += 5
        else:
            print("NO")
            exit()
    else:
        print("NO")
        exit()
print("YES")