The expected output of the case ["10","6","9","3","+","-11","*","/","*","17","+","5","+"] is 22, and the answer in my machine is also 22, but the output of the test is 12.

I don't know what's wrong.

This is my code:

```
class Solution:
# @param tokens, a list of string
# @return an integer
def evalRPN(self, tokens):
stack=[]
for s in tokens:
if s=='+':
op1=stack.pop()
op2=stack.pop()
res=op1+op2
stack.append(res)
elif s=='-':
op1=stack.pop()
op2=stack.pop()
res=op2-op1
stack.append(res)
elif s=='*':
op1=stack.pop()
op2=stack.pop()
res=op2*op1
stack.append(res)
elif s=='/':
op1=stack.pop()
op2=stack.pop()
res=op2/op1
stack.append(int(res))
else:
stack.append(int(s))
return stack.pop()
```