#############################################################

import sys
sys.setrecursionlimit(10**7)

from heapq import heappop,heappush
from collections import deque,defaultdict,Counter
from bisect import bisect_left, bisect_right
from itertools import product,combinations,permutations

ipt = sys.stdin.readline

def iin():
    return int(ipt())
def lmin():
    return list(map(int,ipt().split()))

MOD = 998244353
#############################################################

N,M,K = lmin()
S = input()
if M > N:
    S += "a"*(M-N)

dp = [0]*(27)
F = [0]*26

ans = 0
for i in range(M):
    ndp = [0]*(27)
    s = S[i]
    c = ord(s)-ord("a")
    t = sum(F)

    for j in range(c):
        if F[j]:
            ndp[t] += 1
            ndp[t] %= MOD
        else:
            ndp[t+1] += 1
            ndp[t+1] %= MOD

    for j in range(1,26):
        ndp[j] += dp[j]*j%MOD
        ndp[j] %= MOD
        ndp[j+1] += dp[j]*(26-j)%MOD
        ndp[j+1] %= MOD
    
    ndp[26] += dp[26]*26%MOD
    ndp[26] %= MOD

    F[c] = 1
    dp = ndp
    assert dp[0] == 0

    ans += sum(dp[K:])
    ans %= MOD
    #print(dp)

print(ans)