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.io.BufferedWriter;
	import java.io.IOException;
	import java.io.InputStream;
	import java.io.OutputStream;
	import java.io.OutputStreamWriter;
	import java.io.PrintWriter;
	import java.io.Writer;
	import java.util.Arrays;
	import java.util.InputMismatchException;
	import java.util.*;
	import java.io.*;
	import java.math.*;
	public class Main{

	static class Pair
		{ 
			int x; 
			int y; 
			int z;
			// Constructor 
			public Pair(int x, int y,int z) 
			{	 
				this.x = x; 
				this.y = y; 
				this.z=z;
			}	 
		} 
		static class Compare
		{ 
			static void compare(Pair arr[], int n) 
			{ 
				// Comparator to sort the pair according to second element 
				Arrays.sort(arr, new Comparator<Pair>() { 
					@Override public int compare(Pair p1, Pair p2) 
					{ 
						return p2.z - p1.z; 
					} 
				}); 
			} 
		}
		public static long pow(long a, long b)
		{
			long result=1;
			while(b>0)
			{
				if (b % 2 != 0)
				{
					result=(result*a);
					b--;
				} 
				a=(a*a);
				b /= 2;
			}   
					return result;
		}
		public static BigInteger fact(long num)
		{
					BigInteger fact=new BigInteger("1");
					int i=0;
					for(i=1; i<=num; i++)
					{
						BigInteger bg=BigInteger.valueOf(i);
						fact=fact.multiply(bg);
					}
					return fact;
				}
				public static long gcd(long a, long b)
				{
					if (a == 0)
						return b;
					return gcd(b%a, a);
				}
				
				public static long lcm(int a,int b)
				{
					return a * (b / gcd(a, b));
				}
				public static long sum(int h)
				{
					return (h*(h+1)/2);
				}
				public static void dfs(int parent,boolean[] visited)
				{
					ArrayList<Integer> arr=new ArrayList<Integer>();
				//	arr=graph.get(parent);
					visited[parent]=true;
					for(int i=0;i<arr.size();i++)
					{
						int num=arr.get(i);
						if(visited[num]==false)
						{
							dfs(num,visited);
						}
					}
				}
					
				//static ArrayList<ArrayList<Integer>> graph;
				public static void main(String args[])throws IOException
				{
					InputReader in=new InputReader(System.in);
					OutputWriter out=new OutputWriter(System.out);
				//	long a=pow(26,1000000005);
				//    BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
					ArrayList<Long> ar=new ArrayList<>();
					ArrayList<Integer> ar1=new ArrayList<>();
					ArrayList<Integer> ar2=new ArrayList<>();
					ArrayList<Integer> ar3=new ArrayList<>();
					ArrayList<Integer> ar4=new ArrayList<>();
					TreeSet<Long> ts=new TreeSet<>();
					TreeSet<String> ts1=new TreeSet<>();
					TreeSet<String> pre=new TreeSet<>();
					HashMap<Integer,Integer> hash=new HashMap<>();
					HashMap<Long,Integer> hash1=new HashMap<Long,Integer>();
					HashMap<Long,Integer> hash2=new HashMap<Long,Integer>();
				/*	boolean[] prime=new boolean[100001];
					for(int i=2;i*i<=100000;i++)
					{
						if(prime[i]==false)
						{
							for(int j=2*i;j<=100000;j++)
							{
								prime[j]=true;
							}
						}
					}*/
					int n=i();
					long mod=998244353;
					String s=s();
					char[] ch=s.toCharArray();
					char a=ch[0];
					int count=0,count1=0;
					for(int i=0;i<n;i++)
					{
						if(a==ch[i])
						{
							count++;
						}
						else
						{
							break;
						}
					}
					a=ch[n-1];
					for(int i=n-1;i>=0;i--)
					{
						if(a==ch[i])
						{
							count1++;
						}
						else
							break;
					}
					long ans=0;
					if(ch[0]!=ch[n-1])
					{
						ans+=1*(count1+1);
						for(int j=0;j<count;j++)
						{
							ans++;
						}
						ans=ans%mod;
						pln(ans+"");
					}
					else
					{
						//pln(count+" "+count1);
						if(count==count1 && count+count1==2*n)
						{
							ans=(count)*(count+1)/2;
							ans=ans%mod;
							pln(ans+"");
						}
						else
						{
							ans=(ans%mod+((count+1)%mod*(count1+1)%mod)%mod)%mod;
							pln(ans+"");
						}
					}
				}
	
				
				
				
				
				
				
				
				
				
				
				
				
				
				
				
				
				
				
				
				
				
				
				
				
				
				
				/**/
				static InputReader in=new InputReader(System.in);
					static OutputWriter out=new OutputWriter(System.out);
					public static long l()
					{
						String s=in.String();
						return Long.parseLong(s);
					}
					public static void pln(String value)
					{
						System.out.println(value);
					}
					public static int i()
					{
						return in.Int();
					}
					public static String s()
					{
						return in.String();
					}
		}
			 
			 
			 
			 
			 
			 
			 
			 
			 
			 
			 
			 
			 
			 
			 
			 
			 
			 
			 
			 
			 
			 
			class InputReader {
				 
				private InputStream stream;
				private byte[] buf = new byte[1024];
				private int curChar;
				private int numChars;
				private SpaceCharFilter filter;
			 
				public InputReader(InputStream stream) {
					this.stream = stream;
				}
			 
				public int read() {
					if (numChars== -1)
						throw new InputMismatchException();
					if (curChar >= numChars) {
						curChar = 0;
						try {
							numChars = stream.read(buf);
						} catch (IOException e) {
							throw new InputMismatchException();
						}
						if (numChars <= 0)
							return -1;
					}
					return buf[curChar++];
				}
			 
				public int Int() {
					int c = read();
					while (isSpaceChar(c))
						c = read();
					int sgn = 1;
					if (c == '-') {
						sgn = -1;
						c = read();
					}
					int res = 0;
					do {
						if (c < '0' || c > '9')
							throw new InputMismatchException();
						res *= 10;
						res += c - '0';
						c = read();
					} while (!isSpaceChar(c));
					return res * sgn;
				}
			 
				public String String() {
					int c = read();
					while (isSpaceChar(c))
						c = read();
					StringBuilder res = new StringBuilder();
					do {
						res.appendCodePoint(c);
						c = read();
					} while (!isSpaceChar(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;
				}
			 
				public String next() {
					return String();
				}
			 
				public interface SpaceCharFilter {
					public boolean isSpaceChar(int ch);
				}
			}
			 
			class OutputWriter {
				private final PrintWriter writer;
			 
				public OutputWriter(OutputStream outputStream) {
					writer = new PrintWriter(new BufferedWriter(new OutputStreamWriter(outputStream)));
				}
			 
				public OutputWriter(Writer writer) {
					this.writer = new PrintWriter(writer);
				}
			 
				public void print(Object...objects) {
					for (int i = 0; i < objects.length; i++) {
						if (i != 0)
							writer.print(' ');
						writer.print(objects[i]);
					}
				}
			 
				public void printLine(Object...objects) {
					print(objects);
					writer.println();
				}
			 
				public void close() {
					writer.close();
				}
			 
				public void flush() {
					writer.flush();
				}
			 
				}
			 
				class IOUtils {
			 
				public static int[] readIntArray(InputReader in, int size) {
					int[] array = new int[size];
					for (int i = 0; i < size; i++)
						array[i] = in.Int();
					return array;
				}
			 
				} 