h, w = map(int, input().split())
total = 0
for _ in range(h):
    row = input().strip()
    total += sum(1 - int(c) for c in row)

if total % 2 != 0:
    print("NO")
else:
    if (h-1) * (w-1) % 2 == 0:
        print("YES")
    else:
        print("NO")