while(1):
start = input().strip()
if start==’’:
break
else:
inp = input().strip()
stack = []
conv = {‘C’:12,‘O’:16,‘H’:1}
for i in inp:
if i.isalpha():
stack.append(conv[i])
elif i.isdigit():
stack[-1] = stack[-1]*int(i)
elif i==’(’:
stack.append(’(’)
else:
total = 0
while stack[-1]!=’(’:
total+=stack[-1]
stack.pop()
stack[-1]=total
end = input().strip()
print(sum(stack))
I get nzec error in this code
can anyone help me to find it