user
Explain the following
---
assistant
= raw_input()
n = len(t)
low, high = 0, 0
for i in range(n):
if t[i] == '(':
low += 1
high += 1
elif t[i] == ')':
low -= 1
high -= 1
else:
low -= 1
high += 1
if high < 0:
break
low = max(low, 0)
print("YES" if low == 0 and high >= 0 else "NO")