Buggy python submission (verdict: Time Limit Exceeded):
from collections import deque
from heapq import heapify,heappop,heappush,heappushpop
from copy import copy,deepcopy
from itertools import product,permutations,combinations,combinations_with_replacement
from collections import defaultdict,Counter
from bisect import bisect_left,bisect_right
from math import gcd,ceil,floor,factorial
# from fractions import gcd
from functools import reduce
from pprint import pprint

INF = float("inf")

def myinput():
    return map(int,input().split())

def mylistinput(n):
    return [ list(myinput()) for _ in range(n) ]

def mycol(data,col):
    return [ row[col] for row in data ]

def mysort(data,col,reverse_flag):
    data.sort(key=lambda x:x[col],reverse=reverse_flag)
    return data

def mymax(data):
    M = -1*float("inf")
    for i in range(len(data)):
        m = max(data[i])
        M = max(M,m)
    return M

def mymin(data):
    m = float("inf")
    for i in range(len(data)):
        M = min(data[i])
        m = min(m,M)
    return m

def mycount(ls,x):
    # lsはソート済みであること
    l = bisect_left(ls,x)
    r = bisect_right(ls,x)
    return (r-l)

def myoutput(ls,space=True):
    if space:
        if len(ls)==0:
            print(" ")
        elif type(ls[0])==str:
            print(" ".join(ls))
        elif type(ls[0])==int:
            print(" ".join(map(str,ls)))
        else:
            print("Output Error")
    else:
        if len(ls)==0:
            print("")
        elif type(ls[0])==str:
            print("".join(ls))
        elif type(ls[0])==int:
            print("".join(map(str,ls)))
        else:
            print("Output Error")

def comb_mod_faster(n,k,mod):
    if n<k:
        return 0
    if n<0 or k<0:
        return 0
    k = min(n-k,k)
    ans = 1
    inv = [1]*(k+1)
    if k>=1:
        ans *= (n-k+1)%mod
    for i in range(2,k+1):
        inv[i] = mod - inv[mod%i]*(mod//i)%mod
        ans = ans*(n-k+i)*inv[i]%mod
    return ans

def power_func(a,n,p):
    bi = str(format(n,"b"))#2進表現に
    res = 1
    for i in range(len(bi)):
        res = (res*res) % p
        if bi[i]=="1":
            res = (res*a) % p
    return res

n,m,k = myinput()

mod = 998244353

# ans = 100*(99**99) % mod
# print(ans)

# ls = [0]*(k+1)
# for i in range(k+1):
#     ls[i] = comb_mod_faster(n,i,mod)
# print(ls)

# ans = 0
# for i in range(k+1):
#     t = ls[i]
#     ans += ( (m-1)**(n-t) ) * (m**t)
#     ans %= mod 
# print(ans%mod)

ans = 0
for i in range(k+1):
    t = comb_mod_faster(n-1,i,mod)
    # print(i,t)
    ans1 = power_func(m-1,n-1-i,mod)
    # print(ans1)
    # ans2 = power_func(1,i,mod)
    # print(ans2)
    ans += ( m * t * ans1 ) % mod
    # print(ans)
print(ans%mod)

Fixed submission:
from collections import deque
from heapq import heapify,heappop,heappush,heappushpop
from copy import copy,deepcopy
from itertools import product,permutations,combinations,combinations_with_replacement
from collections import defaultdict,Counter
from bisect import bisect_left,bisect_right
# from math import gcd,ceil,floor,factorial
# from fractions import gcd
from functools import reduce
from pprint import pprint

INF = float("inf")

def myinput():
    return map(int,input().split())

def mylistinput(n):
    return [ list(myinput()) for _ in range(n) ]

def mycol(data,col):
    return [ row[col] for row in data ]

def mysort(data,col,reverse_flag):
    data.sort(key=lambda x:x[col],reverse=reverse_flag)
    return data

def mymax(data):
    M = -1*float("inf")
    for i in range(len(data)):
        m = max(data[i])
        M = max(M,m)
    return M

def mymin(data):
    m = float("inf")
    for i in range(len(data)):
        M = min(data[i])
        m = min(m,M)
    return m

def mycount(ls,x):
    # lsはソート済みであること
    l = bisect_left(ls,x)
    r = bisect_right(ls,x)
    return (r-l)

def myoutput(ls,space=True):
    if space:
        if len(ls)==0:
            print(" ")
        elif type(ls[0])==str:
            print(" ".join(ls))
        elif type(ls[0])==int:
            print(" ".join(map(str,ls)))
        else:
            print("Output Error")
    else:
        if len(ls)==0:
            print("")
        elif type(ls[0])==str:
            print("".join(ls))
        elif type(ls[0])==int:
            print("".join(map(str,ls)))
        else:
            print("Output Error")

def comb_mod_faster(n,k,mod):
    if n<k:
        return 0
    if n<0 or k<0:
        return 0
    k = min(n-k,k)
    ans = 1
    inv = [1]*(k+1)
    if k>=1:
        ans *= (n-k+1)%mod
    for i in range(2,k+1):
        inv[i] = mod - inv[mod%i]*(mod//i)%mod
        ans = ans*(n-k+i)*inv[i]%mod
    return ans

def comb_mod(n, r, mod):
    if n < r:
        return 0
    elif n < 0 or r < 0:
        return 0
    else:
        fac = [1, 1]
        finv = [1, 1]
        inv = [0, 1]
        for i in range(2, n + 1):
            fac.append(fac[-1] * i % mod)
            inv.append(-inv[mod % i] * (mod // i) % mod)
            finv.append((finv[-1] * inv[-1]) % mod)
        return int(fac[n] * finv[r] * finv[n - r] % mod)

def make_comb_mod_list(n,mod):
    r = n
    ls = [0]*(n+1)
    fac = [1, 1]
    finv = [1, 1]
    inv = [0, 1]
    ls[0] = 1
    ls[1] = n
    for i in range(2, n + 1):
        fac.append(fac[-1] * i % mod)
        inv.append(-inv[mod % i] * (mod // i) % mod)
        finv.append((finv[-1] * inv[-1]) % mod)
        ans = int(fac[n] * finv[r] * finv[n - r] % mod)
        ls[i] = ans
    return ls

# nCrをすべてのr(0<=r<=n)について求める
# nC0, nC1, nC2, ... , nCn を求める
# modinvが必要
def combination_list(n, mod=10**9+7):
    lst = [1]
    for i in range(1, n+1):
        lst.append(lst[-1] * (n+1-i) % mod * modinv(i, mod) % mod)
    return lst

def power_func(a,n,p):
    bi = str(format(n,"b"))#2進表現に
    res = 1
    for i in range(len(bi)):
        res = (res*res) % p
        if bi[i]=="1":
            res = (res*a) % p
    return res

class Combination:
    """
    O(n)の前計算を1回行うことで，O(1)でnCr mod mを求められる
    n_max = 10**6のとき前処理は約950ms (PyPyなら約340ms, 10**7で約1800ms)
    使用例：
    comb = Combination(1000000)
    print(comb(5, 3))  # 10
    """
    def __init__(self, n_max, mod=10**9+7):
        self.mod = mod
        self.modinv = self.make_modinv_list(n_max)
        self.fac, self.facinv = self.make_factorial_list(n_max)

    def __call__(self, n, r):
        return self.fac[n] * self.facinv[r] % self.mod * self.facinv[n-r] % self.mod

    def make_factorial_list(self, n):
        # 階乗のリストと階乗のmod逆元のリストを返す O(n)
        # self.make_modinv_list()が先に実行されている必要がある
        fac = [1]
        facinv = [1]
        for i in range(1, n+1):
            fac.append(fac[i-1] * i % self.mod)
            facinv.append(facinv[i-1] * self.modinv[i] % self.mod)
        return fac, facinv

    def make_modinv_list(self, n):
        # 0からnまでのmod逆元のリストを返す O(n)
        modinv = [0] * (n+1)
        modinv[1] = 1
        for i in range(2, n+1):
            modinv[i] = self.mod - self.mod//i * modinv[self.mod%i] % self.mod
        return modinv

n,m,k = myinput()
mod = 998244353

comb = Combination(n,mod)

ans = 0
for i in range(k+1):
    t = comb(n-1,i)
    ans1 = pow(m-1,n-1-i,mod)
    ans += ( m * t * ans1 ) % mod
print(ans%mod)

Buggy python submission (verdict: Time Limit Exceeded):
from collections import deque
from heapq import heapify,heappop,heappush,heappushpop
from copy import copy,deepcopy
from itertools import product,permutations,combinations,combinations_with_replacement
from collections import defaultdict,Counter
from bisect import bisect_left,bisect_right
from math import gcd,ceil,floor,factorial
# from fractions import gcd
from functools import reduce
from pprint import pprint

INF = float("inf")

def myinput():
    return map(int,input().split())

def mylistinput(n):
    return [ list(myinput()) for _ in range(n) ]

def mycol(data,col):
    return [ row[col] for row in data ]

def mysort(data,col,reverse_flag):
    data.sort(key=lambda x:x[col],reverse=reverse_flag)
    return data

def mymax(data):
    M = -1*float("inf")
    for i in range(len(data)):
        m = max(data[i])
        M = max(M,m)
    return M

def mymin(data):
    m = float("inf")
    for i in range(len(data)):
        M = min(data[i])
        m = min(m,M)
    return m

def mycount(ls,x):
    # lsはソート済みであること
    l = bisect_left(ls,x)
    r = bisect_right(ls,x)
    return (r-l)

def myoutput(ls,space=True):
    if space:
        if len(ls)==0:
            print(" ")
        elif type(ls[0])==str:
            print(" ".join(ls))
        elif type(ls[0])==int:
            print(" ".join(map(str,ls)))
        else:
            print("Output Error")
    else:
        if len(ls)==0:
            print("")
        elif type(ls[0])==str:
            print("".join(ls))
        elif type(ls[0])==int:
            print("".join(map(str,ls)))
        else:
            print("Output Error")

def comb_mod_faster(n,k,mod):
    if n<k:
        return 0
    if n<0 or k<0:
        return 0
    k = min(n-k,k)
    ans = 1
    inv = [1]*(k+1)
    if k>=1:
        ans *= (n-k+1)%mod
    for i in range(2,k+1):
        inv[i] = mod - inv[mod%i]*(mod//i)%mod
        ans = ans*(n-k+i)*inv[i]%mod
    return ans

def power_func(a,n,p):
    bi = str(format(n,"b"))#2進表現に
    res = 1
    for i in range(len(bi)):
        res = (res*res) % p
        if bi[i]=="1":
            res = (res*a) % p
    return res

n,m,k = myinput()

mod = 998244353

# ans = 100*(99**99) % mod
# print(ans)

# ls = [0]*(k+1)
# for i in range(k+1):
#     ls[i] = comb_mod_faster(n,i,mod)
# print(ls)

# ans = 0
# for i in range(k+1):
#     t = ls[i]
#     ans += ( (m-1)**(n-t) ) * (m**t)
#     ans %= mod 
# print(ans%mod)

ans = 0
for i in range(k+1):
    t = comb_mod_faster(n-1,i,mod)
    # print(i,t)
    ans1 = power_func(m-1,n-1-i,mod)
    # print(ans1)
    ans2 = power_func(1,i,mod)
    # print(ans2)
    ans += ( m * t * ans1 * ans2 ) % mod
    # print(ans)
print(ans%mod)

Fixed submission:
from collections import deque
from heapq import heapify,heappop,heappush,heappushpop
from copy import copy,deepcopy
from itertools import product,permutations,combinations,combinations_with_replacement
from collections import defaultdict,Counter
from bisect import bisect_left,bisect_right
# from math import gcd,ceil,floor,factorial
# from fractions import gcd
from functools import reduce
from pprint import pprint

INF = float("inf")

def myinput():
    return map(int,input().split())

def mylistinput(n):
    return [ list(myinput()) for _ in range(n) ]

def mycol(data,col):
    return [ row[col] for row in data ]

def mysort(data,col,reverse_flag):
    data.sort(key=lambda x:x[col],reverse=reverse_flag)
    return data

def mymax(data):
    M = -1*float("inf")
    for i in range(len(data)):
        m = max(data[i])
        M = max(M,m)
    return M

def mymin(data):
    m = float("inf")
    for i in range(len(data)):
        M = min(data[i])
        m = min(m,M)
    return m

def mycount(ls,x):
    # lsはソート済みであること
    l = bisect_left(ls,x)
    r = bisect_right(ls,x)
    return (r-l)

def myoutput(ls,space=True):
    if space:
        if len(ls)==0:
            print(" ")
        elif type(ls[0])==str:
            print(" ".join(ls))
        elif type(ls[0])==int:
            print(" ".join(map(str,ls)))
        else:
            print("Output Error")
    else:
        if len(ls)==0:
            print("")
        elif type(ls[0])==str:
            print("".join(ls))
        elif type(ls[0])==int:
            print("".join(map(str,ls)))
        else:
            print("Output Error")

def comb_mod_faster(n,k,mod):
    if n<k:
        return 0
    if n<0 or k<0:
        return 0
    k = min(n-k,k)
    ans = 1
    inv = [1]*(k+1)
    if k>=1:
        ans *= (n-k+1)%mod
    for i in range(2,k+1):
        inv[i] = mod - inv[mod%i]*(mod//i)%mod
        ans = ans*(n-k+i)*inv[i]%mod
    return ans

def comb_mod(n, r, mod):
    if n < r:
        return 0
    elif n < 0 or r < 0:
        return 0
    else:
        fac = [1, 1]
        finv = [1, 1]
        inv = [0, 1]
        for i in range(2, n + 1):
            fac.append(fac[-1] * i % mod)
            inv.append(-inv[mod % i] * (mod // i) % mod)
            finv.append((finv[-1] * inv[-1]) % mod)
        return int(fac[n] * finv[r] * finv[n - r] % mod)

def make_comb_mod_list(n,mod):
    r = n
    ls = [0]*(n+1)
    fac = [1, 1]
    finv = [1, 1]
    inv = [0, 1]
    ls[0] = 1
    ls[1] = n
    for i in range(2, n + 1):
        fac.append(fac[-1] * i % mod)
        inv.append(-inv[mod % i] * (mod // i) % mod)
        finv.append((finv[-1] * inv[-1]) % mod)
        ans = int(fac[n] * finv[r] * finv[n - r] % mod)
        ls[i] = ans
    return ls

# nCrをすべてのr(0<=r<=n)について求める
# nC0, nC1, nC2, ... , nCn を求める
# modinvが必要
def combination_list(n, mod=10**9+7):
    lst = [1]
    for i in range(1, n+1):
        lst.append(lst[-1] * (n+1-i) % mod * modinv(i, mod) % mod)
    return lst

def power_func(a,n,p):
    bi = str(format(n,"b"))#2進表現に
    res = 1
    for i in range(len(bi)):
        res = (res*res) % p
        if bi[i]=="1":
            res = (res*a) % p
    return res

class Combination:
    """
    O(n)の前計算を1回行うことで，O(1)でnCr mod mを求められる
    n_max = 10**6のとき前処理は約950ms (PyPyなら約340ms, 10**7で約1800ms)
    使用例：
    comb = Combination(1000000)
    print(comb(5, 3))  # 10
    """
    def __init__(self, n_max, mod=10**9+7):
        self.mod = mod
        self.modinv = self.make_modinv_list(n_max)
        self.fac, self.facinv = self.make_factorial_list(n_max)

    def __call__(self, n, r):
        return self.fac[n] * self.facinv[r] % self.mod * self.facinv[n-r] % self.mod

    def make_factorial_list(self, n):
        # 階乗のリストと階乗のmod逆元のリストを返す O(n)
        # self.make_modinv_list()が先に実行されている必要がある
        fac = [1]
        facinv = [1]
        for i in range(1, n+1):
            fac.append(fac[i-1] * i % self.mod)
            facinv.append(facinv[i-1] * self.modinv[i] % self.mod)
        return fac, facinv

    def make_modinv_list(self, n):
        # 0からnまでのmod逆元のリストを返す O(n)
        modinv = [0] * (n+1)
        modinv[1] = 1
        for i in range(2, n+1):
            modinv[i] = self.mod - self.mod//i * modinv[self.mod%i] % self.mod
        return modinv

n,m,k = myinput()
mod = 998244353

comb = Combination(n,mod)

ans = 0
for i in range(k+1):
    t = comb(n-1,i)
    ans1 = pow(m-1,n-1-i,mod)
    ans += ( m * t * ans1 ) % mod
print(ans%mod)