Language: C++

#define _CRT_SECURE_NO_WARNINGS
#define _SCL_SECURE_NO_WARNINGS
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cassert>
#include <iostream>
#include <string>
#include <vector>
#include <list>
#include <utility>
#include <algorithm>
#include <functional>
#include <cmath>
#include <stack>
#include <queue>
#include <set>
#include <map>
#include <iomanip>
#include <sstream>
#include <bitset>
#include <limits>
#include <numeric>
#include <valarray>
#include <fstream>

using namespace std;
typedef unsigned int uint;
typedef long long LL;
typedef unsigned long long ULL;
typedef pair<LL, LL> PP;
#define REP(i, a, n) for(LL i = (a), i##_max = (n); i < i##_max; ++i)
#define REM(i, a, n) for(LL i = (LL)(n) - 1, i##min = (a); i >= i##min; --i)
#define ALL(arr) (arr).begin(), (arr).end()
#define FLOAT fixed << setprecision(16)
#define SPEEDUP {cin.tie(NULL); ios::sync_with_stdio(false);}
const int INF = 0x3FFFFFFF;
const LL INFLL = 0x3FFFFFFF3FFFFFFF;
const double INFD = 1.0e+308;
const string INFSTR = "\x7f";
const double EPS = 1.0e-9;

void YesNo(bool b) { cout << (b ? "Yes" : "No") << endl; }
void YESNO(bool b) { cout << (b ? "YES" : "NO") << endl; }
template <class T, class U>
istream& operator>>(istream& ist, pair<T, U>& right) { return ist >> right.first >> right.second; }
template <class T, class U>
ostream& operator<<(ostream& ost, const pair<T, U>& right) { return ost << right.first << ' ' << right.second; }
template <class T, class TCompatible, size_t N>
void Fill(T(&dest)[N], const TCompatible& val) { fill(dest, dest + N, val); }
template <class T, class TCompatible, size_t M, size_t N>
void Fill(T(&dest)[M][N], const TCompatible& val) { for (int i = 0; i < M; ++i) Fill(dest[i], val); }
template<class T>
T Compare(T left, T right) { return left > right ? 1 : (left < right ? -1 : 0); }
istream& Ignore(istream& ist) { string s; ist >> s; return ist; }
bool Inside(int i, int j, int h, int w) { return i >= 0 && i < h && j >= 0 && j < w; }
template <class T>
T Next() { T buf; cin >> buf; return buf; }

#ifdef ONLY_MY_ENVIR
#include "IntMod.h"
#include "UnionFind.h"
#include "Graph.h"
#include "Range.h"
#include "Global.h"
#include "FlowSolver.h"
#include "Tree.h"
#include "SuffixArray.h"
#include "Geometry.h"
#include "Matrix.h"
#include "SegmentTree.h"
#include "SegmentTree2D.h"
#include "BIT.h"
#include "Rational.h"
#include "Position.h"
#include "Factorization.h"
#include "Math.h"
#endif

#ifdef __GNUC__
typedef __int128 LLL;
istream& operator>> (istream& ist, __int128& val) { LL tmp;  ist >> tmp; val = tmp; return ist; }
ostream& operator<< (ostream& ost, __int128 val) { LL tmp = val; ost << tmp; return ost; }
#endif

#if 1234567891
#include <array>
#include <random>
#include <unordered_set>
#include <unordered_map>
template<typename T>
using PriorityQ = priority_queue<T, vector<T>, greater<T> >;
// template <class T>
// auto Is(const T& value) { return [value](const auto& comparand) -> bool { return comparand == value; }; }
#endif

int H, W;
int A[1000];
int B[1000];

int C[1000];

int P[1000000];
int Q[1000000];

int Appear(int a) {
	if (P[a] == -1 && Q[a] == -1) return 0;
	if (P[a] != -1 && Q[a] != -1) return 1;
	if (P[a] != -1) {
		int cnt = 0;
		REP(i, 0, W) {
			cnt += B[i] >= a;
		}
		return cnt;
	}
	if (Q[a] != -1) {
		int cnt = 0;
		REP(i, 0, H) {
			cnt += A[i] >= a;
		}
		return cnt;
	}
}

int main() {
	cin >> H >> W;
	Fill(P, -1);
	Fill(Q, -1);
	REP(i, 0, H) {
		cin >> A[i];
		--A[i];
		if (P[A[i]] != -1) {
			cout << -1 << endl;
			return 0;
		}
		P[A[i]] = i;
	}
	REP(i, 0, W) {
		cin >> B[i];
		--B[i];
		if (Q[B[i]] != -1) {
			cout << -1 << endl;
			return 0;
		}
		Q[B[i]] = i;
	}

	REP(i, 0, H) {
		REP(j, 0, W) {
			int v = min(A[i], B[j]);
			C[v]++;
		}
	}

	MInt prod = 1;
	int cnt = 0;
	REM(i, 0, H * W) {
		cnt += C[i];
		int v = Appear(i);
		if (v != 0) {
			prod *= v;
		} else {
			prod *= cnt;
		}
		cnt -= 1;
	}
	cout << prod << endl;
	return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:155:9: error: 'MInt' was not declared in this scope
  155 |         MInt prod = 1;
      |         ^~~~
a.cc:161:25: error: 'prod' was not declared in this scope
  161 |                         prod *= v;
      |                         ^~~~
a.cc:163:25: error: 'prod' was not declared in this scope
  163 |                         prod *= cnt;
      |                         ^~~~
a.cc:167:17: error: 'prod' was not declared in this scope
  167 |         cout << prod << endl;
      |                 ^~~~
a.cc: In function 'int Appear(int)':
a.cc:123:1: warning: control reaches end of non-void function [-Wreturn-type]
  123 | }
      | ^