H, W = map(int, raw_input().split())
ans = 'NO'
for i in range(0, H):
	s = raw_input()
	for j in range(0, W-4):
		if s[j]=='L' and s[j+1]=='O' and s[j+2]=='V' and s[j+3]=='E':
			ans = 'YES'
			break
	if ans == 'YES': break
print ans