n, m = map(int, raw_input().split())
lst = []
for i in range(0, n):
	lst.append(raw_input())
flag = False
for i in range(0, n):
	for j in range(0, m-3):
		if lst[i][j]=='L' and lst[i][j+1]=='O' and lst[i][j+2]=='V' and lst[i][j+3]=='E':
			flag = True
			break
	if flag: break
if flag: print 'YES'
else: print 'NO'