#include<bits/stdc++.h>
#define PPque priority_queue<tuple<ll, ll, ll>, vector<tuple<ll, ll, ll>>, greater<tuple<ll, ll, ll>>>
#define Pque  priority_queue<pair<ll, ll>, vector<pair<ll, ll>>, greater<pair<ll, ll>>>
#define pque priority_queue<int, vector<int>, greater<int>>
#define umap unordered_map
#define uset unordered_set
#define rep(i, s, f) for(ll i = s; i <= f; i++)
#define per(i, s, f) for(ll i = s; i >= f; i--)
#define all0(x) (x).begin() ,(x).end()
#define all(x) (x).begin() + 1, (x).end()
#define vvvi vector<vector<vector<int>>>
#define vvvl vector<vector<vector<ll>>>
#define vvvc vector<vector<vector<char>>>
#define vvvd vector<vector<vector<double>>>
#define vvi vector<vector<int>>
#define vvl vector<vector<ll>>
#define vvs vector<vector<string>>
#define vvc vector<vector<char>>
#define vvp vector<vector<pair<ll, ll>>>
#define vvb vector<vector<bool>>
#define vvd vector<vector<double>>
#define vp vector<pair<ll, ll>>
#define vi vector<int>
#define vl vector<ll>
#define vs vector<string>
#define vc vector<char>
#define vb vector<bool>
#define vd vector<double>
#define P pair<ll, ll>
#define TU tuple<ll, ll, ll>
#define rrr(l, r) mt()%(r-1)+l+1
#define ENDL '\n'
#define ull unsigned long long
#define debug(a, s) rep(i, s, a.size()-1) {cout << a.at(i) << " ";}cout << endl;
#define Debug(a, s) rep(i, s, a.size()-1) {rep(j, s, a.at(i).size()-1) {cout << a.at(i).at(j) << " ";}cout << endl;}
typedef long long ll;
using namespace std;

////////////////////////////////////////////////////////////////////////////////////////////////////////////
//これが本当の組み込み関数ってね（笑）

template <typename T>
T or_less(vector<T> &A, T x) { //x以下で最大要素の添字 前提: sort済み 存在しない: -1
  return distance(A.begin(), upper_bound(A.begin(), A.end(), x)-1);
}
template <typename T>
T under(vector<T> &A, T x) { //x未満の最大要素の添字　前提: sort済み 存在しない: -1
  return distance(A.begin(), lower_bound(A.begin(), A.end(), x)-1);
}
template <typename T>
T or_more(vector<T> &A, T x) { //x以上で最小要素の添字　　前提: sort済み 存在しない: N .   //distanceのA.beginは添字を出すために常にA.begin() NG: A.begin() + 1
  return distance(A.begin(), lower_bound(A.begin(), A.end(), x));
}
template <typename T>
T over(vector<T> &A, T x) { //xより大きい最小要素の添字前提: sort済み 存在しない: N
  return distance(A.begin(), upper_bound(A.begin(), A.end(), x));
}
void compress(vector<ll> &A) {//小さい順に順位、大きい順にしたいならreverseはNG最後に変換
    vector<ll> temp = A;
    sort(temp.begin()+1, temp.end());
    for (int i = 1; i <= int(A.size()-1); i++) {
        A.at(i) = distance(temp.begin(), lower_bound(temp.begin()+1, temp.end(), A.at(i)));
    }
}
ll LIS1(vl &A) {//at(0)は番兵、広義単調増加
  ll N = A.size()-1;
  vl L(N+1, 1001001001001001001LL);
  L.at(0) = -1 * 1001001001001001001LL;
  ll ans = 0;
  rep(i, 1, N) {
    ll idx = over<ll>(L, A.at(i));
    L.at(idx) = A.at(i);
    ans = max(ans, idx);
  }
  return ans;
}
ll LIS2(vl &A) {//狭義単調増加
  ll N = A.size() - 1;
  vl L(N+1, 1001001001001001001LL);
  L.at(0) = -1 * 1001001001001001001LL;
  ll ans = 0;
  rep(i, 1, N) {
    ll idx = or_more<ll>(L, A.at(i));
    L.at(idx) = A.at(i);
    ans = max(ans, idx);
  }
  return ans;
}
//////////////////////////////////////////////////////////////////////
//数学系
///////////////////////////////////////////////////////////////////////
ll POWER(ll a, ll b, ll mod) {
    a %= mod;
    vector<ll> pow (61);
    pow.at(0) = a;
    bitset<60> bina(b);
    ll answer = 1;
    for (int i = 1; i <= 60; i++) {
      pow.at(i) = pow.at(i-1) * pow.at(i-1) % mod;
        if (bina.test(i-1)) {
            answer = (answer*pow.at(i-1)) % mod;
        }
    }
    return answer;
}
ll Div(ll a, ll b, ll mod) {
    return a * POWER(b, mod-2, mod) % mod;
}

ll round(ll x, ll i) {
    return ll(x + 5 * pow(10, i-1))/ll(pow(10, i)) * ll(pow(10, i));
}
template <typename T> //約分
void normalize(T &mol, T &deno) {
    T mol_temp = abs(mol);
    T deno_temp = abs(deno);
    T GCD = gcd(mol_temp, deno_temp);
    mol /= GCD;
    deno /= GCD;
}
vvl mat_mul(vvl &a, vvl &b, ll mod) {//0-indexed && 正方行列
  ll n = a.size();
  vvl res(n , vl(n, 0));
 
  rep(i, 0, n-1) {
    rep(j, 0, n-1) {
      rep(k, 0, n-1) {
        res.at(i).at(j) += a.at(i).at(k) * b.at(k).at(j);
        res.at(i).at(j) %= mod;
      }
    }
  }
  return res;
}
vvl mat_pow(vvl &a, ll b, ll mod) {//0-indexed && 正方行列
  bitset<60> bina(b);
  vvl power = a;
  int N = a.size();
  vvl res(N, vl(N, 0));
  rep(i, 0, N-1) {
    res.at(i).at(i) = 1;
  }
  rep(i, 1, 60) {
    if (bina.test(i-1)) {
      res = mat_mul(res, power, mod);
    }
    power = mat_mul(power, power, mod);
  }
  return res;
}

vvl comb(ll n, ll mod) {//計算にO(N^2)　読み取りにO(1)
  vvl v(n+1, vl(n+1, 0));
  rep(i, 0, v.size() - 1) {
    v.at(i).at(0) = 1;
    v.at(i).at(i) = 1;
  }

  rep(i, 1, v.size()-1) {
    rep(j, 1, i) {
      v.at(i).at(j) = v.at(i-1).at(j-1) + v.at(i-1).at(j);
      v.at(i).at(j) %= mod;
    }
  }
  return v;
}

ll nCk(int n, int k, ll mod) {//毎回O(max(分子、　分母))
  ll ue = 1;
  ll sita = 1;
  for (int i = 1; i <= k; i++) {
      sita *= i;
      sita %= mod;
  }
  for (int i = 1; i <= k; i++) {
    ue *= (n-i+1);
    ue %= mod;
  }

  return Div(ue, sita, mod);
}
ll cross(P a, P b) {
  return a.first * b.second - a.second * b.first;
}
ll nto10(string S, ll base) {
  ll res = 0;
  reverse(all0(S));
  while(!S.empty()) {
    ll num = S.back() - '0';
    if(num < 0 || num > 9) num = 9 + S.back() - 'a' + 1;
    res = res * base + num;
    S.pop_back();
  }
  return res;
}
string toN(ll N, ll base) {
  if(N == 0) return "0";
  string ans ="";
  ll MOD = abs(base);
  while(N != 0) {
    ll first = N % MOD;
    while(first < 0) first += MOD;
    ans += to_string(first);
    N -= first;
    N /= base;
  }
  reverse(all0(ans));
  return ans;
}
double DIST(P a, P b) {
  return sqrt((a.first - b.first) * (a.first - b.first) + (a.second - b.second) * (a.second - b.second));
}
//////////////////////////////////////////////////////////////////////////////////////////////////////////////
//////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
//グローバル変数を置くところ（情報工学意識高め）
ll int_max = 1001001001;
ll ll_max = 1001001001001001001;
const double pi = 3.141592653589793;
vl dx{0, 1, 0, -1, 0, 1, 1, -1, -1};
vl dy{0, 0, -1, 0, 1, 1, -1, -1, 1};
//#pragma GCC optimize ("-O3")
//ll mod = 1000000007;
ll mod = 998244353;

//////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////


void solve() {
  ll N, M, K;
  cin >> N >> M >> K;
  vvvl dp(M+1, vvl(27, vl(2, 0)));
  dp.at(0).at(0).at(1) = 1;
  string S;
  cin >> S;
  vb used(27, false);

  ll ruiseki = 0;

  rep(i, 1, M) {
    rep(j, 1, 26) {
      if(i <= N) {
        ll now = S.at(i-1) - 'a' + 1;
        ll cnt = 0;
        rep(k, 1, now-1) {
          if(used.at(k))cnt++;
        }
        dp.at(i).at(j).at(0) += dp.at(i-1).at(j).at(1) * cnt;
        dp.at(i).at(j).at(0) += dp.at(i-1).at(j-1).at(1) * (now - 1 - cnt);
        dp.at(i).at(j).at(0) %= mod;
        if(!used.at(now)) {
          ruiseki++;
          used.at(now) = true;
        }
        dp.at(i).at(ruiseki).at(1) = 1;
      }


      dp.at(i).at(j).at(0) += dp.at(i-1).at(j).at(0) * j;
      dp.at(i).at(j).at(0) += dp.at(i-1).at(j-1).at(0) * (26 - j + 1);
      dp.at(i).at(j).at(0) %= mod;
    }
  }

  ll ans = 0;
  rep(i, 1, M) {
    rep(j, K, 26) {
    if(i < N) {
      ans += dp.at(i).at(j).at(1);
    }
    ans += dp.at(i).at(j).at(0);
    ans %= mod;
    }
  }
  cout << ans << endl;




//if(S.at(i) == 1　← 笑）
// modは取りましたか...?(´・ω・｀)
}


int main() {
  ios::sync_with_stdio(false);
  std::cin.tie(nullptr);
  cout << fixed << setprecision(15);
  solve();
  return 0;
}