You are given a string $s$ consisting of lowercase Latin letters. Let the length of $s$ be $|s|$. You may perform several operations on this string.

In one operation, you can choose some index $i$ and remove the $i$-th character of $s$ ($s_i$) if at least one of its adjacent characters is the previous letter in the Latin alphabet for $s_i$. For example, the previous letter for b is a, the previous letter for s is r, the letter a has no previous letters. Note that after each removal the length of the string decreases by one. So, the index $i$ should satisfy the condition $1 \le i \le |s|$ during each operation.

For the character $s_i$ adjacent characters are $s_{i-1}$ and $s_{i+1}$. The first and the last characters of $s$ both have only one adjacent character (unless $|s| = 1$).

Consider the following example. Let $s=$ bacabcab.

1. During the first move, you can remove the first character $s_1=$ b because $s_2=$ a. Then the string becomes $s=$ acabcab.
2. During the second move, you can remove the fifth character $s_5=$ c because $s_4=$ b. Then the string becomes $s=$ acabab.
3. During the third move, you can remove the sixth character $s_6=$'b' because $s_5=$ a. Then the string becomes $s=$ acaba.
4. During the fourth move, the only character you can remove is $s_4=$ b, because $s_3=$ a (or $s_5=$ a). The string becomes $s=$ acaa and you cannot do anything with it.

Your task is to find the maximum possible number of characters you can remove if you choose the sequence of operations optimally.

The first line of the input contains one integer $|s|$ ($1 \le |s| \le 100$) — the length of $s$.

The second line of the input contains one string $s$ consisting of $|s|$ lowercase Latin letters.

Print one integer — the maximum possible number of characters you can remove if you choose the sequence of moves optimally.