'''
Given a binary string s (a string consisting only of '0' and '1's).

Return the number of substrings with all characters 1's.

Since the answer may be too large, return it modulo 10^9 + 7.

 

Example 1:

Input: s = "0110111"
Output: 9
Explanation: There are 9 substring in total with only 1's characters.
"1" -> 5 times.
"11" -> 3 times.
"111" -> 1 time.
Example 2:

Input: s = "101"
Output: 2
Explanation: Substring "1" is shown 2 times in s.
Example 3:

Input: s = "111111"
Output: 21
Explanation: Each substring contains only 1's characters.
Example 4:

Input: s = "000"
Output: 0
 

Constraints:

s[i] == '0' or s[i] == '1'
1 <= s.length <= 10^5
'''
class Solution:
    def numSub(self, s: str) -> int:
        N=len(s)
        sm=0
        def acc(n):
            return (1+n)*n//2
        count=0
        for i in range(N):
            if s[i]=='0':
                # print(i,count)
                sm+=acc(count) % (10**9 + 7)
                count=0
            else:
                count+=1
        sm+=acc(count) % (10**9 + 7)
        return sm
                    