N,M=map(int,input().split())
A=[input() for x in range(N)]

ans=False
for i in range(N):
  for j in range(M-3):
    if A[i][j]=="L" and A[i][j+1]=="O" and A[i][j+2]=="V" and A[i][j+3]=="E":
      ans=True
      break
if ans:
  print("YES")
else:
  print("NO")