Buggy python submission (verdict: Runtime Error):
from collections import deque

direct_l = ((-1, 0), (1, 0), (0, 1), (0, -1))
direct_r = ((1, 0), (-1, 0), (0, 1), (0, -1))
directs = tuple(zip(direct_l, direct_r))

def search(start_l, start_r, mp_l, mp_r):
  que = deque()
  que.append((start_l, start_r))
  dic = {}
  dic[(start_l, start_r)] = True
  while que:
    pl, pr = que.popleft()
    lx, ly = pl
    rx, ry = pr
    for ld, rd in directs:
      ldx, ldy = ld
      rdx, rdy = rd
      lnx, lny = (lx + ldx, ly + ldy) if mp_l[ly + ldy][lx + ldx] != "#" else (lx, ly)
      rnx, rny = (rx + rdx, ry + rdy) if mp_r[ry + rdy][rx + rdx] != "#" else (rx, ry)
      if not ((lnx, lny), (rnx, rny)) in dic:
        dic[((lnx, lny), (rnx, rny))] = True
        if mp_l[lny][lnx] == "%" and mp_r[rny][rnx] == "%":
          print("Yes")
          return
        if mp_l[lny][lnx] != "%" and mp_r[rny][rnx] != "%":
          que.append(((lnx, lny), (rnx, rny)))
  else:
    print("No")
    return


while True:
  w, h = map(int, input().split())
  if w == 0:
    break

  mp_l = ["#" * (w + 2)]
  mp_r = ["#" * (w + 2)]
  for _ in range(h):
    l, r = input().split()
    l = "#" + l + "#"
    r = "#" + r + "#"
    mp_l.append(l)
    mp_r.append(r)
  mp_l.append("#" * (w + 2))
  mp_r.append("#" * (w + 2))
  
  for y in range(1, h + 1):
    for x in range(1, w + 1):
      if mp_l[y][x] == "L":
        start_l = (x, y)
      if mp_r[y][x] == "R":
        start_r = (x, y)

  search(start_l, start_r, mp_l, mp_r)



Fixed submission:
from collections import deque, defaultdict

def main():
  directs = ((-1, 0, 1, 0), (1, 0, -1, 0), (0, 1, 0, 1), (0, -1, 0, -1))
  while True:
    w, h = map(int, input().split())
    if w == 0:
      break
  
    mp_l = ["#" * (w + 2)]
    mp_r = ["#" * (w + 2)]
    for _ in range(h):
      l, r = input().split()
      l = "#" + l + "#"
      r = "#" + r + "#"
      mp_l.append(l)
      mp_r.append(r)
    mp_l.append("#" * (w + 2))
    mp_r.append("#" * (w + 2))
    
    for y in range(1, h + 1):
      for x in range(1, w + 1):
        if mp_l[y][x] == "L":
          start_l = (x, y)
        if mp_r[y][x] == "R":
          start_r = (x, y)
    
    dic = [[[[None] * (h + 2) for _ in range(w + 2)] for _ in range(h + 2)] for _ in range(w + 2)]
    def search():
      que = deque()
      app = que.append
      pop = que.popleft
      app((start_l[0], start_l[1], start_r[0], start_r[1]))
      dic[start_l[0]][start_l[1]][start_r[0]][start_r[1]] = True
      while que:
        lx, ly, rx, ry = pop()
        for ldx, ldy, rdx, rdy in directs:
          ltx, lty, rtx, rty = lx + ldx, ly + ldy, rx + rdx, ry + rdy
          if mp_l[lty][ltx] != "#":
            lnx, lny = ltx, lty
          else:
            lnx, lny = lx, ly
          if mp_r[rty][rtx] != "#":
            rnx, rny = rtx, rty
          else:
            rnx, rny = rx, ry
          tmp = dic[lnx][lny][rnx]
          if not tmp[rny]:
            tmp[rny] = True
            lsym, rsym = mp_l[lny][lnx], mp_r[rny][rnx]
            if lsym == "%":
              if rsym == "%":
                print("Yes")
                return
            elif rsym != "%":
              app(((lnx, lny, rnx, rny)))
      print("No")
      return
    search()
 
main()

Buggy python submission (verdict: Runtime Error):
from collections import deque

direct_l = ((-1, 0), (1, 0), (0, 1), (0, -1))
direct_r = ((1, 0), (-1, 0), (0, 1), (0, -1))
directs = tuple(zip(direct_l, direct_r))

def search(start_l, start_r, mp_l, mp_r, dic):
  que = deque()
  que.append((start_l, start_r))
  dic[start_l[0]][start_l[1]][start_r[0]][start_r[1]] = True
  while que:
    pl, pr = que.popleft()
    lx, ly = pl
    rx, ry = pr
    for ld, rd in directs:
      ldx, ldy = ld
      rdx, rdy = rd
      lnx, lny = (lx + ldx, ly + ldy) if mp_l[ly + ldy][lx + ldx] != "#" else (lx, ly)
      rnx, rny = (rx + rdx, ry + rdy) if mp_r[ry + rdy][rx + rdx] != "#" else (rx, ry)
      if not dic[lnx][lny][rnx][rny]:
        dic[lnx][lny][rnx][rny] = True
        if mp_l[lny][lnx] == "%" and mp_r[rny][rnx] == "%":
          print("Yes")
          return
        if mp_l[lny][lnx] != "%" and mp_r[rny][rnx] != "%":
          que.append(((lnx, lny), (rnx, rny)))
  else:
    print("No")
    return


while True:
  w, h = map(int, input().split())
  if w == 0:
    break

  mp_l = ["#" * (w + 2)]
  mp_r = ["#" * (w + 2)]
  for _ in range(h):
    l, r = input().split()
    l = "#" + l + "#"
    r = "#" + r + "#"
    mp_l.append(l)
    mp_r.append(r)
  mp_l.append("#" * (w + 2))
  mp_r.append("#" * (w + 2))
  
  for y in range(1, h + 1):
    for x in range(1, w + 1):
      if mp_l[y][x] == "L":
        start_l = (x, y)
      if mp_r[y][x] == "R":
        start_r = (x, y)
  #dic[lx][ly][rx][ry]
  dic = [[[[False] * (h + 2) for _ in range(w + 2)] for _ in range(h + 2)] for _ in range(w + 2)]
  search(start_l, start_r, mp_l, mp_r, dic)



Fixed submission:
from collections import deque, defaultdict

def main():
  directs = ((-1, 0, 1, 0), (1, 0, -1, 0), (0, 1, 0, 1), (0, -1, 0, -1))
  while True:
    w, h = map(int, input().split())
    if w == 0:
      break
  
    mp_l = ["#" * (w + 2)]
    mp_r = ["#" * (w + 2)]
    for _ in range(h):
      l, r = input().split()
      l = "#" + l + "#"
      r = "#" + r + "#"
      mp_l.append(l)
      mp_r.append(r)
    mp_l.append("#" * (w + 2))
    mp_r.append("#" * (w + 2))
    
    for y in range(1, h + 1):
      for x in range(1, w + 1):
        if mp_l[y][x] == "L":
          start_l = (x, y)
        if mp_r[y][x] == "R":
          start_r = (x, y)
    
    dic = [[[[None] * (h + 2) for _ in range(w + 2)] for _ in range(h + 2)] for _ in range(w + 2)]
    def search():
      que = deque()
      app = que.append
      pop = que.popleft
      app((start_l[0], start_l[1], start_r[0], start_r[1]))
      dic[start_l[0]][start_l[1]][start_r[0]][start_r[1]] = True
      while que:
        lx, ly, rx, ry = pop()
        for ldx, ldy, rdx, rdy in directs:
          ltx, lty, rtx, rty = lx + ldx, ly + ldy, rx + rdx, ry + rdy
          if mp_l[lty][ltx] != "#":
            lnx, lny = ltx, lty
          else:
            lnx, lny = lx, ly
          if mp_r[rty][rtx] != "#":
            rnx, rny = rtx, rty
          else:
            rnx, rny = rx, ry
          tmp = dic[lnx][lny][rnx]
          if not tmp[rny]:
            tmp[rny] = True
            lsym, rsym = mp_l[lny][lnx], mp_r[rny][rnx]
            if lsym == "%":
              if rsym == "%":
                print("Yes")
                return
            elif rsym != "%":
              app(((lnx, lny, rnx, rny)))
      print("No")
      return
    search()
 
main()

Buggy python submission (verdict: Runtime Error):
from collections import deque

directs = ((-1, 0, 1, 0), (1, 0, -1, 0), (0, 1, 0, 1), (0, -1, 0, -1))

def search(start_l, start_r, mp_l, mp_r, dic):
  que = deque()
  que.append((start_l[0], start_l[1], start_r[0], start_r[1]))
  dic[start_l[0]][start_l[1]][start_r[0]][start_r[1]] = True
  while que:
    lx, ly, rx, ry = que.popleft()
    for ldx, ldy, rdx, rdy in directs:
      lnx, lny = (lx + ldx, ly + ldy) if mp_l[ly + ldy][lx + ldx] != "#" else (lx, ly)
      rnx, rny = (rx + rdx, ry + rdy) if mp_r[ry + rdy][rx + rdx] != "#" else (rx, ry)
      if not dic[lnx][lny][rnx][rny]:
        dic[lnx][lny][rnx][rny] = True
        lsym, rsym = mp_l[lny][lnx], mp_r[rny][rnx]
        if lsym == "%" and rsym == "%":
          print("Yes")
          return
        if lsym != "%" and rsym != "%":
          que.append(((lnx, lny, rnx, rny)))
  else:
    print("No")
    return

def main():
  while True:
    w, h = map(int, input().split())
    if w == 0:
      break
  
    mp_l = ["#" * (w + 2)]
    mp_r = ["#" * (w + 2)]
    for _ in range(h):
      l, r = input().split()
      l = "#" + l + "#"
      r = "#" + r + "#"
      mp_l.append(l)
      mp_r.append(r)
    mp_l.append("#" * (w + 2))
    mp_r.append("#" * (w + 2))
    
    for y in range(1, h + 1):
      for x in range(1, w + 1):
        if mp_l[y][x] == "L":
          start_l = (x, y)
        if mp_r[y][x] == "R":
          start_r = (x, y)
    dic = [[[[False] * (h + 2) for _ in range(w + 2)] for _ in range(h + 2)] for _ in range(w + 2)]
    search(start_l, start_r, mp_l, mp_r, dic)
  
main()


Fixed submission:
from collections import deque, defaultdict

def main():
  directs = ((-1, 0, 1, 0), (1, 0, -1, 0), (0, 1, 0, 1), (0, -1, 0, -1))
  while True:
    w, h = map(int, input().split())
    if w == 0:
      break
  
    mp_l = ["#" * (w + 2)]
    mp_r = ["#" * (w + 2)]
    for _ in range(h):
      l, r = input().split()
      l = "#" + l + "#"
      r = "#" + r + "#"
      mp_l.append(l)
      mp_r.append(r)
    mp_l.append("#" * (w + 2))
    mp_r.append("#" * (w + 2))
    
    for y in range(1, h + 1):
      for x in range(1, w + 1):
        if mp_l[y][x] == "L":
          start_l = (x, y)
        if mp_r[y][x] == "R":
          start_r = (x, y)
    
    dic = [[[[None] * (h + 2) for _ in range(w + 2)] for _ in range(h + 2)] for _ in range(w + 2)]
    def search():
      que = deque()
      app = que.append
      pop = que.popleft
      app((start_l[0], start_l[1], start_r[0], start_r[1]))
      dic[start_l[0]][start_l[1]][start_r[0]][start_r[1]] = True
      while que:
        lx, ly, rx, ry = pop()
        for ldx, ldy, rdx, rdy in directs:
          ltx, lty, rtx, rty = lx + ldx, ly + ldy, rx + rdx, ry + rdy
          if mp_l[lty][ltx] != "#":
            lnx, lny = ltx, lty
          else:
            lnx, lny = lx, ly
          if mp_r[rty][rtx] != "#":
            rnx, rny = rtx, rty
          else:
            rnx, rny = rx, ry
          tmp = dic[lnx][lny][rnx]
          if not tmp[rny]:
            tmp[rny] = True
            lsym, rsym = mp_l[lny][lnx], mp_r[rny][rnx]
            if lsym == "%":
              if rsym == "%":
                print("Yes")
                return
            elif rsym != "%":
              app(((lnx, lny, rnx, rny)))
      print("No")
      return
    search()
 
main()

Buggy python submission (verdict: Runtime Error):
from collections import deque, defaultdict

def main():
  directs = ((-1, 0, 1, 0), (1, 0, -1, 0), (0, 1, 0, 1), (0, -1, 0, -1))
  while True:
    w, h = map(int, input().split())
    if w == 0:
      break
  
    mp_l = ["#" * (w + 2)]
    mp_r = ["#" * (w + 2)]
    for _ in range(h):
      l, r = input().split()
      l = "#" + l + "#"
      r = "#" + r + "#"
      mp_l.append(l)
      mp_r.append(r)
    mp_l.append("#" * (w + 2))
    mp_r.append("#" * (w + 2))
    
    for y in range(1, h + 1):
      for x in range(1, w + 1):
        if mp_l[y][x] == "L":
          start_l = (x, y)
        if mp_r[y][x] == "R":
          start_r = (x, y)
    
    dic = [[[[False] * (h + 2) for _ in range(w + 2)] for _ in range(h + 2)] for _ in range(w + 2)]
    def search():
      que = deque()
      app = que.append
      pop = que.popleft
      app((start_l[0], start_l[1], start_r[0], start_r[1]))
      dic[start_l[0]][start_l[1]][start_r[0]][start_r[1]] = True
      while que:
        lx, ly, rx, ry = pop()
        for ldx, ldy, rdx, rdy in directs:
          lnx, lny = (lx + ldx, ly + ldy) if mp_l[ly + ldy][lx + ldx] != "#" else (lx, ly)
          rnx, rny = (rx + rdx, ry + rdy) if mp_r[ry + rdy][rx + rdx] != "#" else (rx, ry)
          if not dic[lnx][lny][rnx][rny]:
            dic[lnx][lny][rnx][rny] = True
            lsym, rsym = mp_l[lny][lnx], mp_r[rny][rnx]
            if lsym == "%" and rsym == "%":
              print("Yes")
              return
            if lsym != "%" and rsym != "%":
              app(((lnx, lny, rnx, rny)))
      else:
        print("No")
        return
    search()
 
main()


Fixed submission:
from collections import deque, defaultdict

def main():
  directs = ((-1, 0, 1, 0), (1, 0, -1, 0), (0, 1, 0, 1), (0, -1, 0, -1))
  while True:
    w, h = map(int, input().split())
    if w == 0:
      break
  
    mp_l = ["#" * (w + 2)]
    mp_r = ["#" * (w + 2)]
    for _ in range(h):
      l, r = input().split()
      l = "#" + l + "#"
      r = "#" + r + "#"
      mp_l.append(l)
      mp_r.append(r)
    mp_l.append("#" * (w + 2))
    mp_r.append("#" * (w + 2))
    
    for y in range(1, h + 1):
      for x in range(1, w + 1):
        if mp_l[y][x] == "L":
          start_l = (x, y)
        if mp_r[y][x] == "R":
          start_r = (x, y)
    
    dic = [[[[None] * (h + 2) for _ in range(w + 2)] for _ in range(h + 2)] for _ in range(w + 2)]
    def search():
      que = deque()
      app = que.append
      pop = que.popleft
      app((start_l[0], start_l[1], start_r[0], start_r[1]))
      dic[start_l[0]][start_l[1]][start_r[0]][start_r[1]] = True
      while que:
        lx, ly, rx, ry = pop()
        for ldx, ldy, rdx, rdy in directs:
          ltx, lty, rtx, rty = lx + ldx, ly + ldy, rx + rdx, ry + rdy
          if mp_l[lty][ltx] != "#":
            lnx, lny = ltx, lty
          else:
            lnx, lny = lx, ly
          if mp_r[rty][rtx] != "#":
            rnx, rny = rtx, rty
          else:
            rnx, rny = rx, ry
          tmp = dic[lnx][lny][rnx]
          if not tmp[rny]:
            tmp[rny] = True
            lsym, rsym = mp_l[lny][lnx], mp_r[rny][rnx]
            if lsym == "%":
              if rsym == "%":
                print("Yes")
                return
            elif rsym != "%":
              app(((lnx, lny, rnx, rny)))
      print("No")
      return
    search()
 
main()

Buggy python submission (verdict: Runtime Error):
from collections import deque, defaultdict

def main():
  directs = ((-1, 0, 1, 0), (1, 0, -1, 0), (0, 1, 0, 1), (0, -1, 0, -1))
  while True:
    w, h = map(int, input().split())
    if w == 0:
      break
  
    mp_l = ["#" * (w + 2)]
    mp_r = ["#" * (w + 2)]
    for _ in range(h):
      l, r = input().split()
      l = "#" + l + "#"
      r = "#" + r + "#"
      mp_l.append(l)
      mp_r.append(r)
    mp_l.append("#" * (w + 2))
    mp_r.append("#" * (w + 2))
    
    for y in range(1, h + 1):
      for x in range(1, w + 1):
        if mp_l[y][x] == "L":
          start_l = (x, y)
        if mp_r[y][x] == "R":
          start_r = (x, y)
    
    dic = [[[[False] * (h + 2) for _ in range(w + 2)] for _ in range(h + 2)] for _ in range(w + 2)]
    def search():
      que = deque()
      app = que.append
      pop = que.popleft
      app((start_l[0], start_l[1], start_r[0], start_r[1]))
      dic[start_l[0]][start_l[1]][start_r[0]][start_r[1]] = True
      while que:
        lx, ly, rx, ry = pop()
        for ldx, ldy, rdx, rdy in directs:
          if mp_l[ly + ldy][lx + ldx] != "#":
            lnx, lny = lx + ldx, ly + ldy
          else:
            lnx, lny = lx, ly
          if mp_r[ry + rdy][rx + rdx] != "#":
            rnx, rny = rx + rdx, ry + rdy
          else:
            rnx, rny = rx, ry
          #lnx, lny = (lx + ldx, ly + ldy) if mp_l[ly + ldy][lx + ldx] != "#" else (lx, ly)
          #rnx, rny = (rx + rdx, ry + rdy) if mp_r[ry + rdy][rx + rdx] != "#" else (rx, ry)
          if not dic[lnx][lny][rnx][rny]:
            dic[lnx][lny][rnx][rny] = True
            lsym, rsym = mp_l[lny][lnx], mp_r[rny][rnx]
            if lsym == "%" and rsym == "%":
              print("Yes")
              return
            if lsym != "%" and rsym != "%":
              app(((lnx, lny, rnx, rny)))
      else:
        print("No")
        return
    search()
 
main()


Fixed submission:
from collections import deque, defaultdict

def main():
  directs = ((-1, 0, 1, 0), (1, 0, -1, 0), (0, 1, 0, 1), (0, -1, 0, -1))
  while True:
    w, h = map(int, input().split())
    if w == 0:
      break
  
    mp_l = ["#" * (w + 2)]
    mp_r = ["#" * (w + 2)]
    for _ in range(h):
      l, r = input().split()
      l = "#" + l + "#"
      r = "#" + r + "#"
      mp_l.append(l)
      mp_r.append(r)
    mp_l.append("#" * (w + 2))
    mp_r.append("#" * (w + 2))
    
    for y in range(1, h + 1):
      for x in range(1, w + 1):
        if mp_l[y][x] == "L":
          start_l = (x, y)
        if mp_r[y][x] == "R":
          start_r = (x, y)
    
    dic = [[[[None] * (h + 2) for _ in range(w + 2)] for _ in range(h + 2)] for _ in range(w + 2)]
    def search():
      que = deque()
      app = que.append
      pop = que.popleft
      app((start_l[0], start_l[1], start_r[0], start_r[1]))
      dic[start_l[0]][start_l[1]][start_r[0]][start_r[1]] = True
      while que:
        lx, ly, rx, ry = pop()
        for ldx, ldy, rdx, rdy in directs:
          ltx, lty, rtx, rty = lx + ldx, ly + ldy, rx + rdx, ry + rdy
          if mp_l[lty][ltx] != "#":
            lnx, lny = ltx, lty
          else:
            lnx, lny = lx, ly
          if mp_r[rty][rtx] != "#":
            rnx, rny = rtx, rty
          else:
            rnx, rny = rx, ry
          tmp = dic[lnx][lny][rnx]
          if not tmp[rny]:
            tmp[rny] = True
            lsym, rsym = mp_l[lny][lnx], mp_r[rny][rnx]
            if lsym == "%":
              if rsym == "%":
                print("Yes")
                return
            elif rsym != "%":
              app(((lnx, lny, rnx, rny)))
      print("No")
      return
    search()
 
main()