#include <cassert>
#include <cstdio>
#include <cmath>
#include <iostream>
#include <sstream>
#include <string>
#include <vector>
#include <map>
#include <queue>
#include <algorithm>

const int MOD = 1000000007, INF = 1111111111;
using namespace std;
using lint = long long;

template <class T>
ostream &operator<<(ostream &os, const vector<T> &vec) {
	for (int i = 0; i < (int)vec.size(); i++) {
		os << vec[i] << (i + 1 == vec.size() ? "" : " ");
	}
	return os;
}

#ifdef _DEBUG
template <class Head>
void dump(const char* str, Head &&h) { cerr << str << " = " << h << "\n"; };
template <class Head, class... Tail>
void dump(const char* str, Head &&h, Tail &&... t) {
	while (*str != ',') cerr << *str++; cerr << " = " << h << "\n";
	dump(str + 1, t...);
}
#define DMP(...) dump(#__VA_ARGS__, __VA_ARGS__)
#else 
#define DMP(...) ((void)0)
#endif

template<int Modulo = MOD> struct Mint {
	lint val;
	constexpr Mint(lint v = 0) noexcept : val(v % Modulo) {
		if (val < 0) v += Modulo;
	}
	constexpr int getmod() { return Modulo; }
	constexpr Mint operator - () const noexcept { return val ? Modulo - val : 0; }
	constexpr Mint operator + (const Mint& r) const noexcept { return Mint(*this) += r; }
	constexpr Mint operator - (const Mint& r) const noexcept { return Mint(*this) -= r; }
	constexpr Mint operator * (const Mint& r) const noexcept { return Mint(*this) *= r; }
	constexpr Mint operator / (const Mint& r) const noexcept { return Mint(*this) /= r; }
	constexpr Mint& operator += (const Mint& r) noexcept {
		val += r.val;
		if (val >= Modulo) val -= Modulo;
		return *this;
	}
	constexpr Mint& operator -= (const Mint& r) noexcept {
		val -= r.val;
		if (val < 0) val += Modulo;
		return *this;
	}
	constexpr Mint& operator *= (const Mint& r) noexcept {
		val = val * r.val % Modulo;
		return *this;
	}
	constexpr Mint& operator /= (const Mint& r) noexcept {
		lint a = r.val, b = Modulo, u = 1, v = 0, t;
		while (b) {
			t = a / b;
			a -= t * b; swap(a, b);
			u -= t * v; swap(u, v);
		}
		val = val * u % Modulo;
		if (val < 0) val += Modulo;
		return *this;
	}
	constexpr bool operator == (const Mint& r) const noexcept {
		return this->val == r.val;
	}
	constexpr bool operator != (const Mint& r) const noexcept {
		return this->val != r.val;
	}
	friend ostream &operator << (ostream &os, const Mint<Modulo>& x) noexcept {
		return os << x.val;
	}
	friend istream& operator >> (istream &is, Mint<Modulo>& x) noexcept {
		lint tmp; is >> tmp;
		x = Mint<Modulo>(tmp);
		return is;
	}
	friend constexpr Mint<Modulo> modpow(const Mint<Modulo> &a, lint n) noexcept {
		Mint res(1), tmp = a;
		while (n > 0) {
			if (n & 1) res *= tmp;
			tmp *= tmp;
			n >>= 1;
		}
		return res;
	}
};

using mint = Mint<>;

class Combi {
private:
	vector<mint> fac, inv, finv;

	void init(int N) {
		fac[0] = fac[1] = 1; inv[1] = 1; finv[0] = finv[1] = 1;

		for (int i = 2; i < N; i++) {
			fac[i] = fac[i - 1] * i;
			inv[i] = -inv[MOD%i] * (MOD / i);
			finv[i] = finv[i - 1] * inv[i];
		}
	}

public:
	Combi(int N = 100000) : fac(N + 1), inv(N + 1), finv(N + 1) { init(N + 1); }

	mint operator() (int n, int k) {
		if (n < k || k < 0) return 0LL;
		return fac[n] * (finv[k] * finv[n - k]);
	}

	mint Pmod(int n, int k) {
		if (n < k || k < 0) return 0LL;
		return fac[n] * finv[n - k];
	}
};

int main() {

	cin.tie(nullptr);
	ios::sync_with_stdio(false);

	int N, M;
	cin >> N >> M;

	Combi P;
	if (N == M) cout << P.Pmod(N,N) * P.Pmod(M,M) * mint(2) << "\n";
	else if (N == M + 1 || N == M - 1) cout << P.Pmod(N,N) * P.Pmod(M,M) << "\n";
	else cout << 0 << "\n";


	return 0;
}

Measured memory_bytes: 2560