Buggy python submission (verdict: Runtime Error):
n,m,k=map(int,input().split())
MOD=998244353

def prepare(n, MOD):
    # n! の計算
    f = 1
    for m in range(1, n + 1):
        f *= m
        f %= MOD
    fn = f
    # n!^-1 の計算
    inv = pow(f, MOD - 2, MOD)
    # n!^-1 - 1!^-1 の計算
    invs = [1] * (n + 1)
    invs[n] = inv
    for m in range(n, 1, -1):
        inv *= m
        inv %= MOD
        invs[m - 1] = inv
    return fn, invs

a,b=prepare(n-1,MOD)
if n==1:
    print(m)
else:
    ans,s=0,(m*pow(m-1,n-k-2,MOD))%MOD
    for x in range(k,-1,-1):
        s*=(m-1)
        s%=MOD
        ans+=(s*a*b[x]*b[n-x-1])%MOD
        ans%=MOD
    print(ans)

Fixed submission:
n,m,k=map(int,input().split())
MOD=998244353

def prepare(n, MOD):
    # n! の計算
    f = 1
    for m in range(1, n + 1):
        f *= m
        f %= MOD
    fn = f
    # n!^-1 の計算
    inv = pow(f, MOD - 2, MOD)
    # n!^-1 - 1!^-1 の計算
    invs = [1] * (n + 1)
    invs[n] = inv
    for m in range(n, 1, -1):
        inv *= m
        inv %= MOD
        invs[m - 1] = inv
    return fn, invs

a,b=prepare(n-1,MOD)
ans,s=0,(m*pow(m-1,n-k-1,MOD))%MOD
for x in range(k,-1,-1):
    ans+=(s*a*b[x]*b[n-x-1])%MOD
    ans%=MOD
    s*=(m-1)
    s%=MOD
print(ans)

Buggy python submission (verdict: Runtime Error):
n,m,k=map(int,input().split())
MOD=998244353

def prepare(n, MOD):
    # n! の計算
    f = 1
    for m in range(1, n + 1):
        f *= m
        f %= MOD
    fn = f
    # n!^-1 の計算
    inv = pow(f, MOD - 2, MOD)
    # n!^-1 - 1!^-1 の計算
    invs = [1] * (n + 1)
    invs[n] = inv
    for m in range(n, 1, -1):
        inv *= m
        inv %= MOD
        invs[m - 1] = inv
    return fn, invs

a,b=prepare(n-1,MOD)
ans,s=0,(m*pow(m-1,n-k-2,MOD))%MOD
for x in range(k,-1,-1):
    s*=(m-1)
    s%=MOD
    ans+=(s*a*b[x]*b[n-x-1])%MOD
    ans%=MOD
print(ans)

Fixed submission:
n,m,k=map(int,input().split())
MOD=998244353

def prepare(n, MOD):
    # n! の計算
    f = 1
    for m in range(1, n + 1):
        f *= m
        f %= MOD
    fn = f
    # n!^-1 の計算
    inv = pow(f, MOD - 2, MOD)
    # n!^-1 - 1!^-1 の計算
    invs = [1] * (n + 1)
    invs[n] = inv
    for m in range(n, 1, -1):
        inv *= m
        inv %= MOD
        invs[m - 1] = inv
    return fn, invs

a,b=prepare(n-1,MOD)
ans,s=0,(m*pow(m-1,n-k-1,MOD))%MOD
for x in range(k,-1,-1):
    ans+=(s*a*b[x]*b[n-x-1])%MOD
    ans%=MOD
    s*=(m-1)
    s%=MOD
print(ans)

Buggy python submission (verdict: Runtime Error):
import numpy as np
n,m,k=map(int,input().split())
MOD=998244353
dp = np.zeros((n+1,n),dtype=np.int64)
dp[1][0]=m
for i in range(2,n+1):
    dp[i]+=dp[i-1]*(m-1)
    dp[i][1:]+=dp[i-1][:1]
    dp[i]%=MOD
print(sum(dp[n][:k+1]))

Fixed submission:
n,m,k=map(int,input().split())
MOD=998244353

def prepare(n, MOD):
    # n! の計算
    f = 1
    for m in range(1, n + 1):
        f *= m
        f %= MOD
    fn = f
    # n!^-1 の計算
    inv = pow(f, MOD - 2, MOD)
    # n!^-1 - 1!^-1 の計算
    invs = [1] * (n + 1)
    invs[n] = inv
    for m in range(n, 1, -1):
        inv *= m
        inv %= MOD
        invs[m - 1] = inv
    return fn, invs

a,b=prepare(n-1,MOD)
ans,s=0,(m*pow(m-1,n-k-1,MOD))%MOD
for x in range(k,-1,-1):
    ans+=(s*a*b[x]*b[n-x-1])%MOD
    ans%=MOD
    s*=(m-1)
    s%=MOD
print(ans)