human
I found an interesting problem on https://leetcode.com/problems/minimum-remove-to-make-valid-parentheses/:
Given a string s of '(' , ')' and lowercase English characters. 
Your task is to remove the minimum number of parentheses ( '(' or ')', in any positions ) so that the resulting parentheses string is valid and return any valid string.
Formally, a parentheses string is valid if and only if:

It is the empty string, contains only lowercase characters, or
It can be written as AB (A concatenated with B), where A and B are valid strings, or
It can be written as (A), where A is a valid string.

 
Example 1:
Input: s = "lee(t(c)o)de)"
Output: "lee(t(c)o)de"
Explanation: "lee(t(co)de)" , "lee(t(c)ode)" would also be accepted.

Example 2:
Input: s = "a)b(c)d"
Output: "ab(c)d"

Example 3:
Input: s = "))(("
Output: ""
Explanation: An empty string is also valid.

Example 4:
Input: s = "(a(b(c)d)"
Output: "a(b(c)d)"

 
Constraints:

1 <= s.length <= 10^5
s[i] is one of  '(' , ')' and lowercase English letters.

I tried it in Python, but could not do it. Can you solve it?

 Write me a the Python program you requested?
assistant
#Here is the Python program you requested.

class Solution:
    def minRemoveToMakeValid(self, s: str) -> str:
        l, stack= 0, []
        for i in s:
            if i not in ('()'):
                stack.append(i)
            elif i == '(':
                l += 1
                stack.append('(')
            else:
                if l == 0:
                    continue
                else:
                    stack.append(')')
                    l -= 1
        i = len(stack) - 1
        while l > 0 and i >=0:
            if stack[i] == '(':
                stack[i] = ''
                l -= 1
            i -= 1
        return ''.join(stack)