You are given a string s of length n consisting only of lowercase Latin letters.

A substring of a string is a contiguous subsequence of that string. So, string "forces" is substring of string "codeforces", but string "coder" is not.

Your task is to calculate the number of ways to remove exactly one substring from this string in such a way that all remaining characters are equal (the number of distinct characters either zero or one).

It is guaranteed that there is at least two different characters in s.

Note that you can remove the whole string and it is correct. Also note that you should remove at least one character.

Since the answer can be rather large (not very large though) print it modulo 998244353.

If you are Python programmer, consider using PyPy instead of Python when you submit your code.

Input

The first line of the input contains one integer n (2 ≤ n ≤ 2 ⋅ 10^5) — the length of the string s.

The second line of the input contains the string s of length n consisting only of lowercase Latin letters.

It is guaranteed that there is at least two different characters in s.

Output

Print one integer — the number of ways modulo 998244353 to remove exactly one substring from s in such way that all remaining characters are equal.

Examples

Input


4
abaa


Output


6


Input


7
aacdeee


Output


6

Input


2
az


Output


3

Note

Let s[l; r] be the substring of s from the position l to the position r inclusive.

Then in the first example you can remove the following substrings: 

  * s[1; 2]; 
  * s[1; 3]; 
  * s[1; 4]; 
  * s[2; 2]; 
  * s[2; 3]; 
  * s[2; 4]. 



In the second example you can remove the following substrings: 

  * s[1; 4]; 
  * s[1; 5]; 
  * s[1; 6]; 
  * s[1; 7]; 
  * s[2; 7]; 
  * s[3; 7]. 



In the third example you can remove the following substrings: 

  * s[1; 1]; 
  * s[1; 2]; 
  * s[2; 2]. 
# It's never too late to start!
from bisect import bisect_left, bisect_right
import os
import sys
from io import BytesIO, IOBase
from collections import Counter
from collections import deque, defaultdict
import math
import heapq
import re

def sin():
    return input()
def ain():
    return list(map(int, sin().split()))
def sain():
    return input().split()
def iin():
    return int(sin())

LOW = 'abcdefghijklmnopqrstuvwxyz'
UP = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ'
MAX = float('inf')
MIN = float('-inf')
MOD = 998244353

def sieve(n): 
    prime = [True for i in range(n+1)]
    p = 2
    while (p * p <= n): 
        if (prime[p] == True): 
            for i in range(p * p, n+1, p): 
                prime[i] = False
        p += 1
    return prime

# Stay hungry, stay foolish!

def main():
    n = iin()
    s = sin()
    ans = 3
    c1 = 1
    c2 = 1
    for i in range(1,n):
        if s[i] == s[i-1]:
            c1 += 1
            ans += 1
        else:
            break
    for i in range(n-2, -1 ,-1):
        if s[i] == s[i+1]:
            c2 += 1
            ans += 1
        else:
            break 
    ans = ans%MOD
    if n > 1:
        if s[0] == s[-1]:
            x = n-c1-c2 
            if x>0:
                ans += 1
                c1 -= 1
                c2 -= 1
                ans += (c1 + c2)
                if c1!=0 and c2!=0:
                    ans += (c1*c2) 
    print(ans%MOD)







        




        
 


        









    



                    
            








        






    



    
    
    


    

    






            







        
    











            


        













            




        





        






        




        
























    




            
        

        













    
    



# Fast IO Template starts

BUFSIZE = 8192


class FastIO(IOBase):
    newlines = 0
    def __init__(self, file):
        self._fd = file.fileno()
        self.buffer = BytesIO()
        self.writable = "x" in file.mode or "r" not in file.mode
        self.write = self.buffer.write if self.writable else None
    def read(self):
        while True:
            b = os.read(self._fd, max(os.fstat(self._fd).st_size, BUFSIZE))
            if not b:
                break
            ptr = self.buffer.tell()
            self.buffer.seek(0, 2), self.buffer.write(b), self.buffer.seek(ptr)
        self.newlines = 0
        return self.buffer.read()
    def readline(self):
        while self.newlines == 0:
            b = os.read(self._fd, max(os.fstat(self._fd).st_size, BUFSIZE))
            self.newlines = b.count(b"\n") + (not b)
            ptr = self.buffer.tell()
            self.buffer.seek(0, 2), self.buffer.write(b), self.buffer.seek(ptr)
        self.newlines -= 1
        return self.buffer.readline()
    def flush(self):
        if self.writable:
            os.write(self._fd, self.buffer.getvalue())
            self.buffer.truncate(0), self.buffer.seek(0)

class IOWrapper(IOBase):
    def __init__(self, file):
        self.buffer = FastIO(file)
        self.flush = self.buffer.flush
        self.writable = self.buffer.writable
        self.write = lambda s: self.buffer.write(s.encode("ascii"))
        self.read = lambda: self.buffer.read().decode("ascii")
        self.readline = lambda: self.buffer.readline().decode("ascii")

if os.getcwd() == 'D:\\code':
    sys.stdin = open('input.txt', 'r')
    sys.stdout = open('output.txt', 'w')
else:
    sys.stdin, sys.stdout = IOWrapper(sys.stdin), IOWrapper(sys.stdout)
    input = lambda: sys.stdin.readline().rstrip("\r\n")
# Fast IO Template ends

if __name__ == "__main__":
    main()

# Never Give Up - John Cena