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

typedef modint998244353 mint;
typedef long long ll;

#define rep(i, s, n) for (int i = (int)(s); i < (int)(n); i++)
#define rrep(i, s, n) for (int i = (int)(n)-1; i >= (int)(s); i--)

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

int main(){
	// KETA DP
	// small ga kakutei siteiruka?
	// onaji nara?
	int n, m, k; cin >> n >> m >> k;
	string s; cin >> s;
	vector<mint> dp0(27); // small
	vector<mint> dp1(27); // not small
	int tmp = 0;
	vector<bool> snow(26);
	mint ans = 0;
	rep(num,0,m){
		vector<mint> ndp0(27); // small
		vector<mint> ndp1(27); // not small
		rep(j,0,27){
			if (j+1 <= 26) ndp0[j+1] += dp0[j] * (26-j);
			ndp0[j] += dp0[j] * j;
		}
		if (num < n){
			rep(j,0,(int)(s[num] - 'a')){
				if (snow[j]) ndp0[tmp]++;
				else ndp0[tmp+1]++;
				//rep(k,0,27){
				//	if (snow[j]) ndp0[k] += dp1[k];
			//		else ndp0[k+1] += dp1[k];
			//	}
			}
			if (snow[s[num] - 'a']) ndp1[tmp]++;
			else ndp1[tmp+1]++;
			if (!snow[s[num] - 'a']) tmp++;
			snow[s[num] - 'a'] = true;
		}

		dp0 = ndp0;
		dp1 = ndp1;

		rep(i,k,27){
			ans += dp0[i];
			if (num < n-1) ans += dp1[i];
		}

		//cout << ans.val() << '\n';
	}
	//if (tmp >= k) ans--;
	cout << ans.val() << '\n';
}