Given two non-empty strings $$$s$$$ and $$$t$$$, consisting of lowercase Latin letters. Your task is to calculate the number of different pairs of $$$\textbf{(a b)}$$$ such that $$$a$$$ is a substring of string $$$s$$$, $$$b$$$ is a subsequence of string $$$t$$$, and the content of $$$a$$$ and $$$b$$$ is the same. Two pairs are considered different, if they contain different substrings of string $$$s$$$ or different subsequences of string $$$t$$$.

A substring of $$$s$$$ is a non-empty string $$$x = s[a... b] = s_as_{a + 1}... s_b (1 \le a \le b \le |s|)$$$. Two substrings $$$s[a... b]$$$ and $$$s[c... d]$$$ are considered to be different if $$$a ≠ c$$$ or $$$b ≠ d.$$$

A subsequence of $$$s$$$ is a non-empty string $$$y = s[p_1p_2... p_{|y|}] = s_{p_1}s_{p_2}... s_{p_{|y|}} (1 \le p_1 \lt p_2 \lt ... \lt p_{|y|} \le |s|)$$$. Two subsequences $$$u = s[p_1p_2... p_{|u|}]$$$ and $$$v = s[q_1q_2... q_{|v|}]$$$ are considered different if the sequences $$$p$$$ and $$$q$$$ are different.