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.math.*;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.StringTokenizer;

     //--------------->>>>IF YOU ARE HERE FOR QUICKSORT HACK THEN SORRY NO HACK FOR YOU<<<-------------------

public class a{ 
     static int[] count,count1,count2;
     static Node[] nodes;
     static int[] arr;
     static int[] dp;
     static char[] ch,ch1;
     static long[] darr,farr;
     static char[][] mat,mat1;
     static long x,h;
     static long maxl;
     static double dec;
     static long mx = (long)1e9+7;
     static String s;
     static long minl;
     static int start_row;
     static int start_col;     
     static int end_row;     
     static int end_col;     
     static long mod = 998244353;
     // static int minl = -1;
     // static long n;
     static int n,n1,n2;
     static long a;
     static long b;
     static long c;
     static long d;
     static long y,z;
     static int m;
     static long k;
     static String[] str,str1;
     static Set<Integer> set,set1,set2;
     static SortedSet<Long> ss;
     static List<Integer> list,list1,list2,list3;
     static PriorityQueue<Long> pq,pq1;
     static LinkedList<Integer> ll;
     static Map<Integer,List<Integer>> map,map1;
     static StringBuilder sb,sb1,sb2;
     static int index;
     static int[] dx = {0,-1,0,1,-1,1,-1,1};
     static int[] dy = {-1,0,1,0,-1,-1,1,1};

     // public static void solve(){

     //    FastScanner sc = new FastScanner();
     //    // int t = sc.nextInt();
     //    int t = 1;
     //    for(int tt = 0 ; tt < t ; tt++){
     //        int n = sc.nextInt();
     //        int m = sc.nextInt();
     //        int prev = 0;

     //        for(int i = 0 ; i < n ; i++){
     //           int s = sc.nextInt();
     //           int e = sc.nextInt();
     //           if(s > prev){
     //                System.out.println("NO");
     //                return;
     //           }
     //            prev = Math.max(prev,e);
     //        }
     //        if(prev == m)
     //            System.out.println("YES");
     //        else
     //            System.out.println("NO");

     //        // System.out.println(sb);
     //    }
        
        
     // }

     //--------------->>>>IF YOU ARE HERE FOR QUICKSORT HACK THEN SORRY NO HACK FOR YOU<<<-------------------

     public static void solve(){

        long ans = 1;

        int i = 1;
        long pivotLeft = 0;

        while((i < n) && (ch[i] == ch[0]))
            i += 1;

        pivotLeft = i;
        ans += i;

        i = n-2;
        long pivotRight = 0;
        while(i > -1 && ch[i] == ch[n-1])
            i -= 1;

        ans += n-i-1;
        pivotRight = n-i-1;

        if(ch[0] != ch[n-1]){
            System.out.println(ans);
            return;
        }
        if(pivotLeft == n){
            ans = n;
            ans = ((ans)*(ans+1)/2)%mod;
            System.out.println(ans);
            return; 
        }

        ans = (ans + ((pivotLeft * pivotRight)%mod))%mod;
        System.out.println(ans);

     }

     public static void main(String[] args) {

            FastScanner sc = new FastScanner();
            // Scanner sc = new Scanner(System.in);
            // int t = sc.nextInt();
            int t = 1;
            // int l = 1;
            while(t > 0){
                
                // n = sc.nextInt();
                // n = sc.nextLong();
                // a = sc.nextLong();
                // b = sc.nextLong();
                // c = sc.nextLong();
                // d = sc.nextLong();

                // x = sc.nextLong();
                // y = sc.nextLong();
                
                // n = sc.nextLong();
                n = sc.nextInt();
                // n1 = sc.nextInt();

                // m = sc.nextInt();

                // k = sc.nextLong();
                // s = sc.next();

                ch = sc.next().toCharArray();
                // ch1 = sc.next().toCharArray();

                // arr = new int[m];
                // for(int i = 0 ; i < m ; i++){
                //     arr[i] = sc.nextInt();
                // }
                // ch = sc.next().toCharArray();
                // // m = n;
                // darr = new long[m];
                // for(int i = 0 ; i < m ; i++){
                //     darr[i] = sc.nextLong();
                // }

                // farr = new int[n];
                // for(int i = 0; i < n ; i++){
                //     farr[i] = sc.nextInt();
                // }

                // mat = new int[n][n];
                // for(int i = 0 ; i < n ; i++){
                //     for(int j = 0 ;  j < n ; j++){
                //         mat[i][j] = sc.nextInt();
                //     }
                // }

                // mat = new char[n][m];
                // for(int i = 0 ; i < n ; i++){
                //     String s = sc.next();
                //     for(int j = 0 ; j < m ; j++){
                //         mat[i][j] = s.charAt(j);
                //     }
                // }

                // str = new String[n];
                // for(int i = 0 ; i < n ; i++)
                //     str[i] = sc.next();

                // nodes = new Node[n];
                // for(int i = 0 ; i < n ;i++)
                //     nodes[i] = new Node(sc.nextInt(),sc.nextInt());

                // System.out.println(solve()?"YES":"NO");
                 solve();       
                 // System.out.println(solve());
                 t -= 1;
            }

     }

    public static int log(long n){

         if(n == 0 || n == 1)
             return 0;

         if(n == 2)
             return 1;

         double num = Math.log(n);
         double den = Math.log(2);

         if(den == 0)
             return 0;

         return (int)(num/den);
     }

    public static boolean isPrime(long n) { 
    // Corner cases 
        if (n <= 1)  
            return false; 

        if (n <= 3)  
            return true; 
      
        // This is checked so that we can skip  
        // middle five numbers in below loop 
        if (n%2 == 0 || n%3 == 0) 
            return false; 
      
        for (int i=5; i*i<=n; i=i+6) 
            if (n%i == 0 || n%(i+2) == 0) 
               return false; 
      
        return true; 
    } 

     public static long gcd(long a,long b){

        if(b%a == 0){
            return a;
        }
        return gcd(b%a,a);

     }

     // public static void swap(int i,int j){
     //     long temp = arr[j];
     //     arr[j] = arr[i];
     //     arr[i] = temp;
     // } 

    static final Random random=new Random();
    
    static void ruffleSort(long[] a) {
        int n=a.length;//shuffle, then sort 
        for (int i=0; i<n; i++) {
            int oi=random.nextInt(n);
            long temp=a[oi];
            a[oi]=a[i]; a[i]=temp;
        }
        Arrays.sort(a);
    }

    static class Node{
        Integer first;
        Integer second;
        Node(Integer f,Integer s){
            this.first = f;
            this.second = s;
        }
    }

     static class FastScanner {

                BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
                StringTokenizer st=new StringTokenizer("");
                String next() {
                        while (!st.hasMoreTokens())
                                try {
                                        st=new StringTokenizer(br.readLine());
                                } catch (IOException e) {
                                        e.printStackTrace();
                                }
                        return st.nextToken();
                }
                
                int nextInt() {
                        return Integer.parseInt(next());
                }
                int[] readArray(int n) {
                        int[] a=new int[n];
                        for (int i=0; i<n; i++) a[i]=nextInt();
                        return a;
                }
                long nextLong() {
                        return Long.parseLong(next());
                }
        }

}