CF1398C Good Subarrays

You are given an array $ a_1, a_2, \dots , a_n $ consisting of integers from $ 0 $ to $ 9 $ . A subarray $ a_l, a_{l+1}, a_{l+2}, \dots , a_{r-1}, a_r $ is good if the sum of elements of this subarray is equal to the length of this subarray ( $ \sum\limits_{i=l}^{r} a_i = r - l + 1 $ ). For example, if $ a = [1, 2, 0] $ , then there are $ 3 $ good subarrays: $ a_{1 \dots 1} = [1], a_{2 \dots 3} = [2, 0] $ and $ a_{1 \dots 3} = [1, 2, 0] $ . Calculate the number of good subarrays of the array $ a $ .

N/A

N/A

The first test case is considered in the statement. In the second test case, there are $ 6 $ good subarrays: $ a_{1 \dots 1} $ , $ a_{2 \dots 2} $ , $ a_{1 \dots 2} $ , $ a_{4 \dots 4} $ , $ a_{5 \dots 5} $ and $ a_{4 \dots 5} $ . In the third test case there is only one good subarray: $ a_{2 \dots 6} $ .