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

for i in range(N):
    for j in range(M):
        if M <= j+3:
            continue
        elif A[i][j] == 'L':
            if A[i][j+1] == 'O':
                if A[i][j+2] == 'V':
                    if A[i][j+3]== 'E':
                        print('YES')
                        exit()
else:
    print('NO')