#pragma GCC target("avx2")
#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")

#include <algorithm>
#include <atcoder/all>
#include <bitset>
#include <cassert>
#include <cmath>
#include <ctime>
#include <functional>
#include <iomanip>
#include <iostream>
#include <map>
#include <queue>
#include <random>
#include <set>
#include <stack>
#include <string>
#include <tuple>
#include <unordered_map>
#include <unordered_set>
#include <utility>
#include <vector>
using namespace std;
using namespace atcoder;
typedef long long ll;
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define repr(i, n) for (int i = (int)(n)-1; i >= 0; i--)
#define repk(i, k, n) for (int i = k; i < (int)(n); i++)
#define all(v) v.begin(), v.end()
#define mod1 1000000007
#define mod2 998244353
#define mod3 100000007
#define vi vector<int>
#define vs vector<string>
#define vc vector<char>
#define vl vector<ll>
#define vb vector<bool>
#define vvi vector<vector<int>>
#define vvc vector<vector<char>>
#define vvl vector<vector<ll>>
#define vvb vector<vector<bool>>
#define vvvi vector<vector<vector<int>>>
#define vvvl vector<vector<vector<ll>>>
#define pii pair<int, int>
#define pil pair<int, ll>
#define pli pair<ll, int>
#define pll pair<ll, ll>
#define vpii vector<pair<int, int>>
#define vpll vector<pair<ll, ll>>
#define vvpii vector<vector<pair<int, int>>>
#define vvpll vector<vector<pair<ll, ll>>>

using mint = modint998244353;

template <typename T>
void debug(T e) {
    cerr << e << endl;
}

template <typename T>
void debug(vector<T> &v) {
    rep(i, v.size()) { cerr << v[i] << " "; }
    cerr << endl;
}

template <typename T>
void debug(vector<vector<T>> &v) {
    rep(i, v.size()) {
        rep(j, v[i].size()) { cerr << v[i][j] << " "; }
        cerr << endl;
    }
}

template <typename T>
void debug(vector<pair<T, T>> &v) {
    rep(i, v.size()) { cerr << v[i].first << " " << v[i].second << endl; }
}

template <typename T>
void debug(set<T> &st) {
    for (auto itr = st.begin(); itr != st.end(); itr++) {
        cerr << *itr << " ";
    }
    cerr << endl;
}

template <typename T>
void debug(multiset<T> &ms) {
    for (auto itr = ms.begin(); itr != ms.end(); itr++) {
        cerr << *itr << " ";
    }
    cerr << endl;
}

template <typename T>
void debug(map<T, T> &mp) {
    for (auto itr = mp.begin(); itr != mp.end(); itr++) {
        cerr << itr->first << " " << itr->second << endl;
    }
}

void debug_out() { cerr << endl; }

template <typename Head, typename... Tail>
void debug_out(Head H, Tail... T) {
    cerr << H << " ";
    debug_out(T...);
}

ll my_pow(ll x, ll n, ll mod) {
    // 　繰り返し二乗法．x^nをmodで割った余り．
    ll ret;
    if (n == 0) {
        ret = 1;
    } else if (n % 2 == 1) {
        ret = (x * my_pow((x * x) % mod, n / 2, mod)) % mod;
    } else {
        ret = my_pow((x * x) % mod, n / 2, mod);
    }
    return ret;
}

ll inv(ll x, ll mod) { return my_pow(x, mod - 2, mod); }

int main() {
    ll N, M, K;
    cin >> N >> M >> K;
    string S;
    cin >> S;
    vector<ll> ns(N);
    for (ll i = 0; i < N; i++) {
        ns[i] = (ll)(S[i] - 'a');
    }
    vector<vector<ll>> dp1(M, vector<ll>(27, 0));
    vector<vector<ll>> dp2(M, vector<ll>(27, 0));
    dp2[0][1] = ns[0];
    dp1[0][1] = 1;
    ll now_kind = 1;
    vector<ll> kinds(26, 0);
    kinds[ns[0]]++;

    for (ll i = 1; i < N; i++) {
        if (kinds[ns[i]] == 0) {
            now_kind++;
        }
        kinds[ns[i]]++;
        dp1[i][now_kind] = 1;
        for (ll j = 1; j <= 26; j++) {
            dp2[i][j] = (dp2[i][j] + dp2[i - 1][j] * j) % mod2;
            dp2[i][j] = (dp2[i][j] + dp2[i - 1][j - 1] * (26 - (j - 1))) % mod2;
        }
        ll up = 0;
        ll down = 0;
        for (ll j = 0; j < ns[i]; j++) {
            if (kinds[j] == 0) {
                down++;
            } else {
                up++;
            }
        }
        for (ll j = 1; j <= 26; j++) {
            dp2[i][j] = (dp2[i][j] + dp1[i - 1][j] * up) % mod2;
            dp2[i][j] = (dp2[i][j] + dp1[i - 1][j - 1] * down) % mod2;
        }
    }
    for (ll i = N; i < M; i++) {
        for (ll j = 1; j <= 26; j++) {
            dp2[i][j] = (dp2[i][j] + (dp2[i - 1][j] * j)) % mod2;
            dp2[i][j] = (dp2[i][j] + dp2[i - 1][j - 1] * (26 - (j - 1))) % mod2;
        }
    }
    ll ans = 0;
    for (ll i = 0; i < M; i++) {
        for (ll j = K; j <= 26; j++) {
            ans = (ans + dp2[i][j]) % mod2;
        }
    }
    for (ll i = 0; i < N - 1; i++) {
        for (ll j = K; j <= 26; j++) {
            ans = (ans + dp1[i][j]) % mod2;
        }
    }
    // debug(dp1);
    // debug(dp2);
    cout << ans << endl;
}