S=input().split(' ')
n=int(S[0])
m=int(S[1])
k=0
for i in range(n):
    A=input()
    for j in range(m-3):
        if(A[j]=='L' and A[j+1]=='O' and A[j+2]=='V' and A[j+3]=='E'):
           k=k+1

if( k > 0):
   print('YES')
else:
    print('NO')