Buggy python submission (verdict: Runtime Error):
# coding: utf-8
import sys
sys.setrecursionlimit(1000000)
N,M,K=map(int,input().split())
MOD=998244353

MAX_N=N

#a**n mod p を再帰的に求める
def modPow(a,n,p):
    if n==0:
        return 1
    if n == 1:
        #n=1ならaを返す
        return a % p

    elif n % 2 == 1:
        #nが奇数ならば a * modPow(a,n-1(偶数),p)を返す
        return a * modPow(a,n-1,p) % p

    else:
        #nが偶数なら modPow(a,n//2,p) * modPow(a,n//2,p)とすると速い
        t = modPow(a,n//2,p)
        return t * t % p

fac=[None for i in range(MAX_N)]
finv=[None for i in range(MAX_N)]
inv=[None for i in range(MAX_N)]

def COMinit(num):
    global fac
    global finv
    global inv
    fac[0]=1
    fac[1]=1
    finv[0]=1
    finv[1]=1
    inv[1]=1

    for i in range(2,num):
        fac[i] = fac[i-1] * i % MOD
        inv[i] = MOD - inv[MOD%i] * (MOD // i) % MOD
        finv[i] = finv[i-1] * inv[i] % MOD

def COM(n,k):
    if n<k:
        return 0
    elif n<0 or k<0:
        return 0
    else:
        return int(fac[n] * (finv[k] * finv[n - k] % MOD) % MOD)


COMinit(MAX_N)

ans=0

for i in range(K+1):
    v=COM(N-1,N-1-K+i)%MOD
    v*=M
    v=v%MOD
    v*=modPow(M-1,N-1-K+i,MOD)
    v=v%MOD
    ans+=v
    ans=ans%MOD
print(ans)

Fixed submission:
# coding: utf-8
import sys
sys.setrecursionlimit(1000000)
N,M,K=map(int,input().split())
MOD=998244353

MAX_N=N+10

#a**n mod p を再帰的に求める
def modPow(a,n,p):
    if n==0:
        return 1
    if n == 1:
        #n=1ならaを返す
        return a % p

    elif n % 2 == 1:
        #nが奇数ならば a * modPow(a,n-1(偶数),p)を返す
        return a * modPow(a,n-1,p) % p

    else:
        #nが偶数なら modPow(a,n//2,p) * modPow(a,n//2,p)とすると速い
        t = modPow(a,n//2,p)
        return t * t % p

fac=[None for i in range(MAX_N)]
finv=[None for i in range(MAX_N)]
inv=[None for i in range(MAX_N)]

def COMinit(num):
    global fac
    global finv
    global inv
    fac[0]=1
    fac[1]=1
    finv[0]=1
    finv[1]=1
    inv[1]=1

    for i in range(2,num):
        fac[i] = fac[i-1] * i % MOD
        inv[i] = MOD - inv[MOD%i] * (MOD // i) % MOD
        finv[i] = finv[i-1] * inv[i] % MOD

def COM(n,k):
    if n<k:
        return 0
    elif n<0 or k<0:
        return 0
    else:
        return int(fac[n] * (finv[k] * finv[n - k] % MOD) % MOD)


COMinit(MAX_N)

ans=0

for i in range(K+1):
    v=COM(N-1,N-1-K+i)%MOD
    v*=M
    v=v%MOD
    v*=modPow(M-1,N-1-K+i,MOD)
    v=v%MOD
    ans+=v
    ans=ans%MOD
print(ans)

Buggy python submission (verdict: Runtime Error):
# coding: utf-8
import sys
sys.setrecursionlimit(1000000000)
N,M,K=map(int,input().split())
MOD=998244353

MAX_N=10**6

#a**n mod p を再帰的に求める
def modPow(a,n,p):
    if n == 1:
        #n=1ならaを返す
        return a % p

    elif n % 2 == 1:
        #nが奇数ならば a * modPow(a,n-1(偶数),p)を返す
        return a * modPow(a,n-1,p) % p

    else:
        #nが偶数なら modPow(a,n//2,p) * modPow(a,n//2,p)とすると速い
        t = modPow(a,n//2,p)
        return t * t % p

fac=[None for i in range(MAX_N)]
finv=[None for i in range(MAX_N)]
inv=[None for i in range(MAX_N)]

def COMinit(num):
    global fac
    global finv
    global inv
    fac[0]=1
    fac[1]=1
    finv[0]=1
    finv[1]=1
    inv[1]=1

    for i in range(2,num):
        fac[i] = fac[i-1] * i % MOD
        inv[i] = MOD - inv[MOD%i] * (MOD // i) % MOD
        finv[i] = finv[i-1] * inv[i] % MOD

def COM(n,k):
    if n<k:
        return 0
    elif n<0 or k<0:
        return 0
    else:
        return int(fac[n] * (finv[k] * finv[n - k] % MOD) % MOD)


COMinit(MAX_N)

ans=0

for i in range(K+1):
    ans+=COM(N-1,N-1-K+i)*M*modPow(M-1,N-1-K+i,MOD)
    ans=ans%MOD
print(ans)

Fixed submission:
# coding: utf-8
import sys
sys.setrecursionlimit(1000000)
N,M,K=map(int,input().split())
MOD=998244353

MAX_N=N+10

#a**n mod p を再帰的に求める
def modPow(a,n,p):
    if n==0:
        return 1
    if n == 1:
        #n=1ならaを返す
        return a % p

    elif n % 2 == 1:
        #nが奇数ならば a * modPow(a,n-1(偶数),p)を返す
        return a * modPow(a,n-1,p) % p

    else:
        #nが偶数なら modPow(a,n//2,p) * modPow(a,n//2,p)とすると速い
        t = modPow(a,n//2,p)
        return t * t % p

fac=[None for i in range(MAX_N)]
finv=[None for i in range(MAX_N)]
inv=[None for i in range(MAX_N)]

def COMinit(num):
    global fac
    global finv
    global inv
    fac[0]=1
    fac[1]=1
    finv[0]=1
    finv[1]=1
    inv[1]=1

    for i in range(2,num):
        fac[i] = fac[i-1] * i % MOD
        inv[i] = MOD - inv[MOD%i] * (MOD // i) % MOD
        finv[i] = finv[i-1] * inv[i] % MOD

def COM(n,k):
    if n<k:
        return 0
    elif n<0 or k<0:
        return 0
    else:
        return int(fac[n] * (finv[k] * finv[n - k] % MOD) % MOD)


COMinit(MAX_N)

ans=0

for i in range(K+1):
    v=COM(N-1,N-1-K+i)%MOD
    v*=M
    v=v%MOD
    v*=modPow(M-1,N-1-K+i,MOD)
    v=v%MOD
    ans+=v
    ans=ans%MOD
print(ans)

Buggy python submission (verdict: Runtime Error):
# coding: utf-8
import sys
sys.setrecursionlimit(1000000)
N,M,K=map(int,input().split())
MOD=998244353


#a**n mod p を再帰的に求める
def modPow(a,n,p):
    if n == 1:
        #n=1ならaを返す
        return a % p

    elif n % 2 == 1:
        #nが奇数ならば a * modPow(a,n-1(偶数),p)を返す
        return a * modPow(a,n-1,p) % p

    else:
        #nが偶数なら modPow(a,n//2,p) * modPow(a,n//2,p)とすると速い
        t = modPow(a,n//2,p)
        return t * t % p

fac=[None for i in range(N)]
finv=[None for i in range(N)]
inv=[None for i in range(N)]

def COMinit(num):
    global fac
    global finv
    global inv
    fac[0]=1
    fac[1]=1
    finv[0]=1
    finv[1]=1
    inv[1]=1

    for i in range(2,num):
        fac[i] = fac[i-1] * i % MOD
        inv[i] = MOD - inv[MOD%i] * (MOD // i) % MOD
        finv[i] = finv[i-1] * inv[i] % MOD

def COM(n,k):
    if n<k:
        return 0
    elif n<0 or k<0:
        return 0
    else:
        return int(fac[n] * (finv[k] * finv[n - k] % MOD) % MOD)


COMinit(N)

ans=0

for i in range(K+1):
    ans+=COM(N-1,N-1-K+i)*M*modPow(M-1,N-1-K+i,MOD)
    ans=ans%MOD
print(ans)

Fixed submission:
# coding: utf-8
import sys
sys.setrecursionlimit(1000000)
N,M,K=map(int,input().split())
MOD=998244353

MAX_N=N+10

#a**n mod p を再帰的に求める
def modPow(a,n,p):
    if n==0:
        return 1
    if n == 1:
        #n=1ならaを返す
        return a % p

    elif n % 2 == 1:
        #nが奇数ならば a * modPow(a,n-1(偶数),p)を返す
        return a * modPow(a,n-1,p) % p

    else:
        #nが偶数なら modPow(a,n//2,p) * modPow(a,n//2,p)とすると速い
        t = modPow(a,n//2,p)
        return t * t % p

fac=[None for i in range(MAX_N)]
finv=[None for i in range(MAX_N)]
inv=[None for i in range(MAX_N)]

def COMinit(num):
    global fac
    global finv
    global inv
    fac[0]=1
    fac[1]=1
    finv[0]=1
    finv[1]=1
    inv[1]=1

    for i in range(2,num):
        fac[i] = fac[i-1] * i % MOD
        inv[i] = MOD - inv[MOD%i] * (MOD // i) % MOD
        finv[i] = finv[i-1] * inv[i] % MOD

def COM(n,k):
    if n<k:
        return 0
    elif n<0 or k<0:
        return 0
    else:
        return int(fac[n] * (finv[k] * finv[n - k] % MOD) % MOD)


COMinit(MAX_N)

ans=0

for i in range(K+1):
    v=COM(N-1,N-1-K+i)%MOD
    v*=M
    v=v%MOD
    v*=modPow(M-1,N-1-K+i,MOD)
    v=v%MOD
    ans+=v
    ans=ans%MOD
print(ans)