Rikka with New Year's Party

Rikka is now organizing a new year's party for the algorithm association. She has invited $n$ actors from 26 different groups, represented by lowercase letters. Rikka wants to select some actors among them for the opening show.

Now, the $n$ actors are in a row. The $i$-th actor is from the $s_i$-th group. Rikka decides to choose a non-empty range $[l,r]$ ($1 \leq l \leq r \leq n$) and lets all actors in this range join the opening show.

The show proceeds as follows.

• The actors play in order. The $l$-th actor plays first, and the $r$-th actor plays last.
• When the $i$-th actor is about to play, they decide their action as follows. If an actor $j$ who played before them is from the same group $s_i$, the $i$-th actor chooses the same action as actor $j$. Otherwise, they choose the action with the smallest index that no one has chosen before.

For example, if the 5 actors are from groups abacb, they choose actions $1,2,1,3,2$ in that order.

Rikka found that different ranges can produce the same show. For example, if there are 6 actors from groups abacbc, the ranges $[1,3]$ and $[4,6]$ produce the same show.

Two shows are different if they have different numbers of actions, or if some index $i$ has different $i$-th actions. A show is possible if some range $[l,r]$ of $s$ produces it. Given $s$, count the number of different possible shows.

The first line contains a single integer $n$ ($1 \leq n \leq 10^5$), the number of actors.

The second line contains a lowercase string $s$ of length $n$. $s_i$ is the group of the $i$-th actor.

Output a single integer on one line, the number of different possible shows.

For the first sample, there are 7 different possible shows:

1. Action $1$, corresponding to ranges $[1,1]$, $[2,2]$, $[3,3]$, $[4,4]$, $[5,5]$.
2. Actions $1,2$, corresponding to ranges $[1,2]$, $[2,3]$, $[3,4]$, $[4,5]$.
3. Actions $1,2,1$, corresponding to ranges $[1,3]$, $[2,4]$.
4. Actions $1,2,3$, corresponding to range $[3,5]$.
5. Actions $1,2,1,2$, corresponding to range $[1,4]$.
6. Actions $1,2,1,3$, corresponding to range $[2,5]$.
7. Actions $1,2,1,2,3$, corresponding to range $[1,5]$.