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]. 
"""
Author    : co_devil Chirag Garg
Institute : JIIT
"""

from __future__ import division, print_function
import itertools, os, sys, threading
from collections import deque, Counter, OrderedDict, defaultdict
# from heapq import nsmallest, nlargest, heapify, #heappop ,heappush, heapreplace
from math import ceil,floor,log,sqrt,factorial,pow,pi
# from bisect import bisect_left,bisect_right
# from decimal import *,threading
"""from io import BytesIO, IOBase
if sys.version_info[0] < 3:
    from __builtin__ import xrange as range
    from future_builtins import ascii, filter, hex, map, oct, zip
else:
    from builtins import str as __str__
    str = lambda x=b'': x if type(x) is bytes else __str__(x).encode()
BUFSIZE = 8192
class FastIO(IOBase):
    newlines = 0
    def __init__(self, file):
        self._buffer = BytesIO()
        self._fd = file.fileno()
        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):
        return self._buffer.read() if self._buffer.tell() else os.read(self._fd, os.fstat(self._fd).st_size)

    def readline(self):
        while self.newlines == 0:
            b, ptr = os.read(self._fd, max(os.fstat(self._fd).st_size, BUFSIZE)), self._buffer.tell()
            self._buffer.seek(0, 2), self._buffer.write(b), self._buffer.seek(ptr)
            self.newlines += b.count(b'\n') + (not b)
        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)
sys.stdin, sys.stdout = FastIO(sys.stdin), FastIO(sys.stdout)
input = lambda: sys.stdin.readline().rstrip(b'\r\n')

def print(*args, **kwargs):
    sep, file = kwargs.pop('sep', b' '), kwargs.pop('file', sys.stdout)
    at_start = True
    for x in args:
        if not at_start:
            file.write(sep)
        file.write(str(x))
        at_start = False
    file.write(kwargs.pop('end', b'\n'))
    if kwargs.pop('flush', False):
        file.flush()

"""


def ii(): return int(input())
def si(): return str(input())
def mi(): return map(int,input().split())
def li(): return list(mi())


abc = 'abcdefghijklmnopqrstuvwxyz'
abd = {'a': 0, 'b': 1, 'c': 2, 'd': 3, 'e': 4, 'f': 5, 'g': 6, 'h': 7, 'i': 8, 'j': 9, 'k': 10, 'l': 11, 'm': 12,
       'n': 13, 'o': 14, 'p': 15, 'q': 16, 'r': 17, 's': 18, 't': 19, 'u': 20, 'v': 21, 'w': 22, 'x': 23, 'y': 24,
       'z': 25}
mod = 1000000007
dx, dy = [-1, 1, 0, 0], [0, 0, 1, -1]
def getKey(item): return item[0]
def sort2(l): return sorted(l, key=getKey)
def d2(n, m, num): return [[num for x in range(m)] for y in range(n)]
def isPowerOfTwo(x): return (x and (not (x & (x - 1))))
def decimalToBinary(n): return bin(n).replace("0b", "")
def ntl(n): return [int(i) for i in str(n)]
def powerMod(x, y, p):
    res = 1
    x %= p
    while y > 0:
        if y & 1:
            res = (res * x) % p
        y = y >> 1
        x = (x * x) % p1
    return res
def gcd(x, y):
    while y:
        x, y = y, x % y
    return x
# For getting input from input.txt file
# sys.stdin = open('input.txt', 'r')

# Printing the Output to output.txt file
# sys.stdout = open('output.txt', 'w')

graph = defaultdict(list)
visited = [0] * 1000000
col = [-1] * 1000000
def dfs(v, c):
    if visited[v]:
        if col[v] != c:
            print('-1')
            exit()
        return
    col[v] = c
    visited[v] = 1
    for i in graph[v]:
        dfs(i, c ^ 1)

def bfs(d,v):
    q=[]
    q.append(v)
    visited[v]=1
    while len(q)!=0:
        x=q[0]
        q.pop(0)
        for i in d[x]:
            if visited[i]!=1:
                visited[i]=1
                q.append(i)
        print(x)
def make_graph():
    d={}
    v,e=mi()
    for i in range(e):
        x,y=mi()
        if x not in d.keys():
            d[x]=[y]
        else:
            d[x].append(y)
        if y not in d.keys():
            d[y] = [x]
        else:
            d[y].append(x)
    return d
def gr2(l,n):
    d={}
    for i in range(1,n+1):
        if i not in d.keys():
            d[i]=l[i]
        else:
            d[i].append(l[i])
    return d

n=ii()
s=si()
r = 1
l = 1

for i in range(1, n):
    if s[0] == s[i]:
        l += 1
    else:
        break

for i in range(2, n):
    if s[-1] == s[-i]:
        r += 1
    else:
        break

if s[0] == s[-1]:
    print(((l + 1) * (r + 1)) % 998244353)
else:
    print((l + r + 1) % 998244353)