#include <bits/stdc++.h>
#define cs const
#define pb push_back
using namespace std;

cs int N = 2e5 + 5; 

using ll = long long; 
cs int mod = 998244353; 

int n, k; 
char S[N];

ll S1, S2, S3, S4; 

ll work(int a, int b, int c, int d) {
    ll sum = 1ll * a * b % mod * S1 % mod; 
    sum += 1ll * a * d % mod * S2 % mod; 
    sum += 1ll * c * b % mod * S3 % mod; 
    sum += 1ll * c * d % mod * S4 % mod; 
    return sum % mod; 
}

int main() {
    #ifdef zqj
    freopen("1.in","r",stdin);
    #endif
    cin >> n >> k; 
    scanf("%s", S + 1);
    vector <int> sw(n + 1), sc(n + 1);
    for(int i = 1; i <= n; i++) {
        sw[i] = sw[i - 1] + (S[i] == 'W');
        sc[i] = sc[i - 1] + (S[i] == 'C');
    }
    for(int i = 1; i <= k; i++) {
        S1 = (S1 + 1ll * (i - 1) * (k - i)) % mod;
        S2 = (S2 + 1ll * (i - 1) * (k - i + 1)) % mod; 
        S3 = (S3 + 1ll * i * (k - i)) % mod; 
        S4 = (S4 + 1ll * i * (k - i + 1)) % mod; 
    }
    int Sw = 0, Sc = 0; 
    ll ans = 0; 
    for(int i = n; i; i --) {
        Sw += (S[i] == 'W');
        Sc += (S[i] == 'C');
        if(S[i] == 'A') ans = (ans + work(Sw, sc[i], sw[i], Sc)) % mod; 
    }
    cout << ans << '\n';
}