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]. 
import java.util.*;
import java.io.*;
import java.lang.reflect.Array;

		public class codeforces
		{	
			public static void main(String[] args)
			{
				InputReader in = new InputReader(System.in);
				PrintWriter pw = new PrintWriter(System.out);
			
				int n = in.nextInt();
				String s = in.nextLine();
				char l, r;
				long ans = 0, min = 0, countl = 0, countr = 0, M = 998244353;
				
				l = s.charAt(0);
				r = s.charAt(n-1);
				
				int j = 0;
				
				while(s.charAt(j) == l)
				{
					countl++;
					j++;
				}
				
				j = n-1;
				
				while(s.charAt(j) == r)
				{
					countr++;
					j--;
				}
				
				min = Math.min(countl, countr);
				
				if(l == r)
					ans = (countl + 1)*(countr + 1);
				else
					ans = countl + countr + 1;
				
				pw.println(ans%M);
				
				pw.flush();
				pw.close();
			}
			
			public static ArrayList Divisors(int n)
			{
			    ArrayList<Integer> div = new ArrayList<>();
			    
			    for (int i=1; i<=Math.sqrt(n); i++)
			    {
			        if (n%i == 0)
			        {
			        	div.add(i);
			                
			            if(n/i != i)
			            	div.add(n/i);
			        }
			    }
			    return div;
			}
			
			/*public static void DFS(int s)
			{
				int count = 0;
				visited[s] = true;
				
				for(int u : adj[s])
				{
					if(!visited[u])
					{
						count++;
						DFS(u);
					}
				}
				
				if(s == 1 && count == 1)
					leaf++;
				
				if(count == 0)
					leaf++;
			}*/
			
			public static int BinarySearch(long[] a, long k)
			{
				int n = a.length;
				int i = 0, j = n-1;
				int mid = 0;
				
				if(k < a[0])
					return 0;
				else if(k >= a[n-1])
					return n;
				else
				{
					while(j - i > 1)
					{
						mid = (i+j)/2;
						
						if(k >= a[mid])
							i = mid;
						else
							j = mid;
					}
				}
				
				return i+1;
			}
			public static long GCD(long a,long b)
			{
				if(b==0)
					return a;
				else
					return GCD(b,a%b);
			}
			
			static class pair implements Comparable<pair>
			{
				Integer x, y;
				pair(int x,int y)
				{
					this.x=x;
					this.y=y;
				}
				
				public int compareTo(pair o) {
					int result = x.compareTo(o.x);
					if(result==0)
						result = y.compareTo(o.y);
					
					return result;
				}  
				
				public String toString()
				{
					return x+" "+y;
				}
				
				public boolean equals(Object o)
				{
					if (o instanceof pair)
				    {
						pair p = (pair)o;
						return p.x - x == 0 && p.y - y == 0 ;
					}
					return false;
				}
				
				public int hashCode()
				{
					return new Long(x).hashCode()*31 + new Long(y).hashCode();
				}
			}
			
			static class InputReader 
			{
				 
				private final InputStream stream;
				private final byte[] buf = new byte[8192];
				private int curChar, snumChars;
				private SpaceCharFilter filter;
		 
				public InputReader(InputStream stream) 
				{
					this.stream = stream;
				}
		 
				public int snext() 
				{
					if (snumChars == -1)
						throw new InputMismatchException();
					if (curChar >= snumChars) 
					{
						curChar = 0;
						try 
						{
							snumChars = stream.read(buf);
						} 
						catch (IOException e) 
						{
							throw new InputMismatchException();
						}
						if (snumChars <= 0)
							return -1;
					}
					return buf[curChar++];
				}
		 
				public int nextInt() 
			    {
					int c = snext();
					while (isSpaceChar(c)) 
					{
						c = snext();
					}
					int sgn = 1;
					if (c == '-')
				    {
						sgn = -1;
						c = snext();
					}
					int res = 0;
					do 
					{
						if (c < '0' || c > '9')
							throw new InputMismatchException();
						res *= 10;
						res += c - '0';
						c = snext();
					} while (!isSpaceChar(c));
					return res * sgn;
				}
		 
				public long nextLong()
			    {
					int c = snext();
					while (isSpaceChar(c)) 
					{
						c = snext();
					}
					int sgn = 1;
					if (c == '-') 
					{
						sgn = -1;
						c = snext();
					}
					long res = 0;
					do 
					{
						if (c < '0' || c > '9')
							throw new InputMismatchException();
						res *= 10;
						res += c - '0';
						c = snext();
					} while (!isSpaceChar(c));
					return res * sgn;
				}
		 
				public int[] nextIntArray(int n) 
				{
					int a[] = new int[n];
					for (int i = 0; i < n; i++) 
					{
						a[i] = nextInt();
					}
					return a;
				}
		 
				public String readString()
			    {
					int c = snext();
					while (isSpaceChar(c)) 
					{
						c = snext();
					}
					StringBuilder res = new StringBuilder();
					do 
					{
						res.appendCodePoint(c);
						c = snext();
					} while (!isSpaceChar(c));
					return res.toString();
				}
		 
				public String nextLine() 
				{
					int c = snext();
					while (isSpaceChar(c))
						c = snext();
					StringBuilder res = new StringBuilder();
					do 
					{
						res.appendCodePoint(c);
						c = snext();
					} while (!isEndOfLine(c));
					return res.toString();
				}
		 
				public boolean isSpaceChar(int c) 
				{
					if (filter != null)
						return filter.isSpaceChar(c);
					return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
				}
		 
				private boolean isEndOfLine(int c) 
				{
					return c == '\n' || c == '\r' || c == -1;
				}
		 
				public interface SpaceCharFilter
			    {
					public boolean isSpaceChar(int ch);
				}
			}
			
			static class CodeX {
	        public static void sort(long arr[]) {
	            merge_sort(arr, 0, arr.length - 1);
	        }
	
	        private static void merge_sort(long A[], long start, long end) {
	            if (start < end) {
	                long mid = (start + end) / 2;
	                merge_sort(A, start, mid);
	                merge_sort(A, mid + 1, end);
	                merge(A, start, mid, end);
	            }
	
	        }
	
	        private static void merge(long A[], long start,long mid, long end) {
	            long p = start, q = mid + 1;
	            long Arr[] = new long[(int)(end - start + 1)];
	            long k = 0;
	
	            for (int i = (int)start; i <= end; i++) {
	                if (p > mid)
	                    Arr[(int)k++] = A[(int)q++];
	
	                else if (q > end)
	                    Arr[(int)k++] = A[(int)p++];
	
	                else if (A[(int)p] < A[(int)q])
	                    Arr[(int)k++] = A[(int)p++];
	
	                else
	                    Arr[(int)k++] = A[(int)q++];
	            }
	            for (int i = 0; i < k; i++) {
	                A[(int)start++] = Arr[i];
	            }
	
	        }
	
	    }
		}	
		

			