#include<bits/stdc++.h>
using namespace std;

#define all(v) v.begin(),v.end()
using ll = long long;
using ull = unsigned long long;
using vll=vector<ll>;
using vvll = vector<vector<ll>>;
using P = pair<ll,ll>;
using vp=vector<pair<ll, ll>>;

const ll INF=1ll<<60;
ll mod10=1e9+7;
ll mod99=998244353;
const double PI = acos(-1);

#define rep(i,n) for (ll i=0;i<n;++i)
#define per(i,n) for(ll i=n-1;i>=0;--i)
#define rep2(i,a,n) for (ll i=a;i<n;++i)
#define per2(i,a,n) for (ll i=a;i>=n;--i)

template <typename T>
bool chmax(T &a,const T& b){
    if(a<b){
        a=b;
        return true;
    }
    return false;
}

template <typename T>
bool chmin(T &a,const T& b){
    if(a>b){
        a=b;
        return true;
    }
    return false;
}

int main(){
    ll N,M,K;
    cin>>N>>M>>K;
    string S;
    cin>>S;
    vector<vvll> dp(M+1,vvll(2,vll(30)));
    dp[0][0][0]=1;
    set<int> st;
    rep(i,M){
        rep(k,27){
            if(i<N){
                if(st.count(S[i]))dp[i+1][0][k]+=dp[i][0][k];
                else dp[i+1][0][k+1]+=dp[i][0][k];
                dp[i+1][1][k+1]+=dp[i][1][k]*(26-k);
                dp[i+1][1][k]+=dp[i][1][k]*k;
                ll cnt0=0,cnt1=0;
                rep(s,S[i]-'a'){
                    if(st.count(s+'a'))cnt1++;
                    else cnt0++;
                }
                dp[i+1][1][k+1]+=dp[i][0][k]*cnt0;
                dp[i+1][1][k]+=dp[i][0][k]*cnt1;
            }else{
                dp[i+1][1][k+1]+=dp[i][1][k]*(26-k);
                dp[i+1][1][k]+=dp[i][1][k]*k;
            }
            dp[i+1][1][k]%=mod99;
            dp[i+1][1][k+1]%=mod99;
            dp[i+1][0][k]%=mod99;
            dp[i+1][0][k+1]%=mod99;
        }
        st.insert(S[i]);
    }
    ll ans=0;
    rep(i,M+1) rep2(k,K,27) ans=(ans+dp[i][1][k])%mod99;
    cout << ans << endl;

}