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

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 = S+"a"*(M-N)

dp = [0]*(K+1)
F = [0]*26

ans = 0
for i in range(M):
    ndp = [0]*(K+1)
    s = S[i]
    c = ord(s)-ord("a")
    t = sum(F)

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

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

    F[c] = 1
    dp = ndp

    ans += dp[K]
    if sum(F) >= K and i < N-1:
        ans += 1
    ans %= MOD

print(ans)