#include <algorithm>
#include <bit>
#include <bitset>
#include <cassert>
#include <cstdio>
#include <cstdlib>
#include <cmath>
#include <deque>
#include <iostream>
#include <map>
#include <random>
#include <unordered_set>
#include <unordered_map>
#include <vector>
#include <set>
#include <string>

using namespace::std;

template<typename T, typename U>
ostream& operator<< (ostream& o, const pair<T, U>& p) {
  o << "<" << p.first << ", " << p.second << ">";
  return o;
}

template <typename T>
ostream& operator<< (ostream& o, const vector<T>& v) {
 for (const auto& x : v) o << x << " ";
 return o;
}

template <typename T>
ostream& operator<< (ostream& o, const set<T>& v) {
 for (const auto& x : v) o << x << " ";
 return o;
}

template <typename T>
ostream& operator<< (ostream& o, const deque<T>& v) {
 for (const auto& x : v) o << x << " ";
 return o;
}

template <typename K, typename V>
ostream& operator<<(ostream& o, const unordered_map<K, V>& m) {
  o << "{";
  for (const auto& [k, v] : m)
    o << " " << k << ": " << v << ",";
  o << "}";
  return o;
}

template <typename T>
istream& operator>> (istream& i, vector<T>& v) {
  for (auto& x : v) i >> x;
  return i;
}

istream& operator>> (istream& i, pair<int, int>& p) {
  i >> p.first >> p.second;
  return i;
}



int main() {
  ios::sync_with_stdio(false);
  long long n, m, k;
  string s;
  cin >> n >> m >> k >> s;
  const long long p = 998244353;
  long long r = 0;
  bitset<32> present;
  vector<vector<long long>> lowered(m + 1, vector<long long>('z' - 'a' + 1));
  
  for (int l = 1; l <= m; ++l) {
    if (l <= n) {
      char c = s[l - 1];
      int i = c - 'a';
      bitset<32> lower = (1 << i) - 1;
    
      lowered[l][present.count()] += (lower & present).count(); 
      lowered[l][present.count()] %= p;
    
      lowered[l][present.count() + 1] += (lower & ~present).count();
      lowered[l][present.count() + 1] %= p;
    
      present.set(i);
    }
    
    for (int j = 0; j <= ('z' - 'a' + 1); ++j) {
      lowered[l][j] += (lowered[l - 1][j] * j) % p;
      lowered[l][j] %= p;
      
      if (j > 0) {
        lowered[l][j] += (lowered[l - 1][j - 1] * ('z' - 'a' + 1 - (j - 1))) % p;
        lowered[l][j] %= p;
      }
    }
    
    for (int j = k; j <= ('z' - 'a' + 1); ++j)
      r = (r + lowered[l][j]) % p;
  }
  
  //cerr << lowered << endl;
  cout << r << endl;
  return 0;
}