ICPC and Typos#10828
Typos are a very important part of ICPC problem statements. ICPC research department found out that there exist main categories of typos:
One letter of the word was accidentally skipped (for example, sell is written instead of shell)
One extra letter was accidentally inserted (for example, horny is written instead of horn)
One letter was accidentally replaced with another (for example, ictc is written instead of icpc)
ICPC research department now considers an alphabet consisting of first Latin letters and a word . They wonder: how many distinct words can you obtain by making in exactly one typo?
The first line contains a single integer (1 \le n \le 26) — the size of the alphabet.
The second line contains a string (2 \le |s| \le 100000), which consists only of the first letters of the Latin alphabet.
Output the number of distinct words that you can obtain by making in exactly one typo.
Note that the word with typos can contain only letters among the first letters of the Latin alphabet, too. For example, for n = 3 and cab you can't obtain dab by mistyping c.
Example 1
From the string abcd from the sample we can obtain the following strings:
abc abd acd bcd
aacd abad abbd abca
abcb abcc abdd accd
adcd bbcd cbcd dbcd
aabcd abacd abbcd abcad
abcbd abccd abcda abcdb
abcdc abcdd abdcd acbcd
adbcd babcd cabcd dabcd