/**
 * code generated by JHelper
 * More info: https://github.com/AlexeyDmitriev/JHelper
 * @author aryssoncf
 */



// Taken from: https://github.com/bqi343/USACO/blob/master/Implementations/content/contest/templateShort.cpp

#include <utility>
#include <vector>
#include <random>
#include <chrono>
#include <cassert>
#include <set>
#include <queue>
#include <map>
#include <numeric>
#include <algorithm>
#include <iostream>
#include <unordered_map>
#include <bitset>
#include <iomanip>
#include <complex>
#include <stack>
#include <array>
#include <unordered_set>

using namespace std;

typedef long long ll;
typedef unsigned long long ull;
typedef long double ld;
typedef double db;
typedef string str;

typedef pair<int, int> pii;

typedef vector<int> vi;
typedef vector<ull> vul;
typedef vector<ll> vl;
typedef vector<pii> vpii;

#define FOR(i,a,b) for (int i = (a); i < (b); ++i)
#define F0R(i,a) FOR(i,0,a)
#define ROF(i,a,b) for (int i = (b)-1; i >= (a); --i)
#define R0F(i,a) ROF(i,0,a)
#define trav(a,x) for (auto& a: x)

#define sz(x) (int)x.size()
#define all(x) begin(x), end(x)
#define rsz resize

#define mp make_pair
#define pb push_back
#define f first
#define s second

const int MOD = 1e9+7; // 998244353; // = (119<<23)+1
const int MX = 2e5+5;

template<class T> bool ckmin(T& a, const T& b) {
    return a > b ? a = b, 1 : 0; }
template<class T> bool ckmax(T& a, const T& b) {
    return a < b ? a = b, 1 : 0; }

mt19937 rng((uint32_t)chrono::steady_clock::now().time_since_epoch().count());


//
// Created by aryssoncf on 28/10/2019.
//

#include <type_traits>


#include <iterator>


template <typename T>
constexpr auto hasBegin(int) -> decltype(std::begin(std::declval<T>()), true) {
    return true;
}

constexpr bool hasBegin(...) {
    return false;
}

template <typename T>
using IsContainer = std::integral_constant<bool, hasBegin<T>(0)>;


#ifndef JHELPER_EXAMPLE_PROJECT_IO_HPP
#define JHELPER_EXAMPLE_PROJECT_IO_HPP

#endif //JHELPER_EXAMPLE_PROJECT_IO_HPP

template<typename T>
std::istream &operator>>(std::istream &is, std::vector<T> &vec) {
    for (T &element: vec) {
        is >> element;
    }
    return is;
}

template<typename T, typename U>
std::istream &operator>>(std::istream &is, std::pair<T, U> &p) {
    is >> p.first;
    is >> p.second;
    return is;
}

template <class X, class Y>
std::ostream & operator << (std::ostream & os, std::pair <X, Y> const& p) {
    return os << p.first << " " << p.second;
}

template <class Ch, class Tr, class Container>
std::basic_ostream <Ch, Tr> & operator << (std::basic_ostream <Ch, Tr>& os, Container const& x) {
    bool first = true;
    for(auto& y : x) {
        if (first) {
            first = false;
        } else {
            os << " ";
        }
        os << y;
    }
    return os;
}



#include <assert.h>



#include <string>
#include <stdexcept>

#ifndef SPCPPL_ASSERT
#ifdef SPCPPL_DEBUG
#define SPCPPL_ASSERT(condition) \
		if(!(condition)) { \
			throw std::runtime_error(std::string() + #condition + " in line " + std::to_string(__LINE__) + " in " + __PRETTY_FUNCTION__); \
		}
#else
#define SPCPPL_ASSERT(condition)
#endif
#endif





template <typename T, typename = std::true_type>
struct IdentityHelper;

template <typename T>
struct IdentityHelper<T, typename std::is_arithmetic<T>::type> {
    static T identity() {
        return 1;
    }
};

template <typename T>
T identity() {
    return IdentityHelper<T>::identity();
}



/**
* ax + by = result
*/
template <typename T>
T extendedGcd(T a, T b, T& x, T& y) {
    if (a == 0) {
        x = 0;
        y = 1;
        return b;
    }
    T d = extendedGcd(b % a, a, y, x);
    x -= (b / a) * y;
    return d;
}

template <typename T>
class Zn {
public:
    Zn(): value(0) {
    }

    Zn(int64_t value): value(value) {
        int x = static_cast<int>(value % mod());
        if (x < 0) {
            x += mod();
        }
        this->value = x;
    }

    template <typename U>
    static Zn valueOf(U value) {
        int x = static_cast<int>(value % mod());
        if (x < 0) {
            x += mod();
        }
        return Zn(x);
    }

    static Zn rawValueOf(int value) {
        SPCPPL_ASSERT(value >= 0 && value < mod());
        return Zn(value);
    }

    template <typename U>
    Zn& operator=(U rhs) {
        return *this = Zn::valueOf(rhs);
    }


    Zn& operator+=(const Zn& rhs) {
        value += rhs.value;
        if (value >= mod()) {
            value -= mod();
        }
        return *this;
    }

    template <typename U>
    Zn& operator+=(U rhs) {
        return *this += Zn::valueOf(rhs);
    }

    Zn& operator-=(const Zn& rhs) {
        value -= rhs.value;
        if (value < 0) {
            value += mod();
        }
        return *this;
    }

    template <typename U>
    Zn& operator-=(U rhs) {
        return *this -= Zn::valueOf(rhs);
    }

    Zn& operator*=(const Zn& rhs) {
        long long result = static_cast<int64_t>(value) * static_cast<int64_t>(rhs.value);
        value = static_cast<int>(result % mod());
        return *this;
    }

    template <typename U>
    Zn& operator*=(U rhs) {
        return *this *= Zn::valueOf(rhs);
    }

    Zn operator-() const {
        if (value == 0) {
            return *this;
        }
        else {
            return Zn(mod() - value);
        }
    }

    Zn& operator/=(const Zn& rhs) {
        return *this *= rhs.inversed();
    }

    template <typename U>
    Zn& operator/=(U rhs) {
        return *this /= Zn::valueOf(rhs);
    }

    Zn inv() const {
        return inversed();
    }

    inline Zn inversed() const {
        SPCPPL_ASSERT(value != 0);

        int x, y;
        int gcd = extendedGcd(value, mod(), x, y);
        (void) gcd;
        SPCPPL_ASSERT(gcd == 1);

        if (x < 0) {
            x += mod();
        }
        return Zn(x);
    }

    template <typename U>
    friend std::ostream& operator<<(std::ostream&, const Zn<U>& zn);

    template <typename U>
    friend std::istream& operator>>(std::istream&, Zn<U>& zn);

    template <typename U>
    friend bool operator==(const Zn<U>& lhs, const Zn<U>& rhs);

    int intValue() const {
        return value;
    }

    operator int64_t() const {
        return value;
    }

    constexpr static int mod() {
        return T::value;
    }

private:
    int value;

    template <int N = T::value>
    static constexpr bool correct_or_runtime(int) {
        return N > 0 && N <= (1 << 30);
    }
    static constexpr bool correct_or_runtime(...) {
        return true;
    }
    static_assert(
            std::is_same<typename std::decay<decltype(T::value)>::type, int>::value,
            "T::value must be int"
    );
    static_assert(correct_or_runtime(0), "Mod has to be positive integer up to 1 << 30");
};

template <typename T>
bool operator==(const Zn<T>& lhs, const Zn<T>& rhs) {
    return lhs.value == rhs.value;
}

template <typename T, typename U>
bool operator==(const Zn<T>& lhs, U rhs) {
    return lhs == Zn<T>::valueOf(rhs);
}

template <typename T, typename U>
bool operator==(U lhs, const Zn<T>& rhs) {
    return rhs == lhs;
}

template <typename T>
bool operator!=(const Zn<T>& lhs, const Zn<T>& rhs) {
    return !(lhs == rhs);
}

template <typename T, typename U>
bool operator!=(const Zn<T>& lhs, U rhs) {
    return !(lhs == rhs);
}

template <typename T, typename U>
bool operator!=(U lhs, const Zn<T>& rhs) {
    return !(lhs == rhs);
}

template <typename T>
Zn<T> operator+(const Zn<T>& lhs, const Zn<T>& rhs) {
    Zn<T> copy = lhs;
    return copy += rhs;
}

template <typename T, typename U>
Zn<T> operator+(const Zn<T>& lhs, U rhs) {
    Zn<T> copy = lhs;
    return copy += rhs;
}

template <typename T, typename U>
Zn<T> operator+(U lhs, const Zn<T>& rhs) {
    return rhs + lhs;
}

template <typename T>
Zn<T> operator-(const Zn<T>& lhs, const Zn<T>& rhs) {
    Zn<T> copy = lhs;
    return copy -= rhs;
}

template <typename T, typename U>
Zn<T> operator-(const Zn<T>& lhs, U rhs) {
    Zn<T> copy = lhs;
    return copy -= rhs;
}

template <typename T, typename U>
Zn<T> operator-(U lhs, const Zn<T>& rhs) {
    return Zn<T>::valueOf(lhs) - rhs;
}

template <typename T>
Zn<T> operator*(const Zn<T>& lhs, const Zn<T>& rhs) {
    Zn<T> copy = lhs;
    return copy *= rhs;
}

template <typename T, typename U>
Zn<T> operator*(const Zn<T>& lhs, U rhs) {
    Zn<T> copy = lhs;
    return copy *= rhs;
}

template <typename T, typename U>
Zn<T> operator*(U lhs, const Zn<T>& rhs) {
    return rhs * lhs;
}

template <typename T>
Zn<T> operator/(const Zn<T>& lhs, const Zn<T>& rhs) {
    Zn<T> copy = lhs;
    return copy /= rhs;
}

template <typename T, typename U>
Zn<T> operator/(const Zn<T>& lhs, U rhs) {
    Zn<T> copy = lhs;
    return copy /= rhs;
}

template <typename T, typename U>
Zn<T> operator/(U lhs, const Zn<T>& rhs) {
    return Zn<T>::valueOf(lhs) / rhs;
}

template <typename T>
std::ostream& operator<<(std::ostream& stream, const Zn<T>& zn) {
    return stream << zn.value;
}

template <typename T>
std::istream& operator>>(std::istream& stream, Zn<T>& zn) {
    int64_t value;
    stream >> value;
    zn.value = static_cast<int>(value % T::value);
    return stream;
}

template <typename T>
struct IdentityHelper<Zn<T>> {
    static Zn<T> identity() {
        return Zn<T>::valueOf(1);
    }
};

template <int m>
using ZnConst = Zn<std::integral_constant<int, m>>;

using Zn7 = ZnConst<1000000007>;

using namespace std;

class CReconciled {
public:
	void solve(std::istream& in, std::ostream& out) {
        int n, m;
        in >> n >> m;
        if (n < m) {
            swap(n, m);
        }
        vector<Zn7> fac(n + 1);
        fac[0] = 1;
        FOR(i, 1, n + 1) {
            fac[i] = fac[i - 1] * i;
        }
        Zn7 res = fac[n] * fac[m];
        if (n == m) {
            res *= 2;
        } else if (n > m + 1) {
            res = 0;
        }
        out << res << '\n';
	}

	void setup() {}
};


int main() {
    std::ios_base::sync_with_stdio(false);
	CReconciled solver;
    solver.setup();
	std::istream& in(std::cin);
	std::ostream& out(std::cout);
	in.tie(nullptr);
    out << std::fixed;
    out.precision(20);
	solver.solve(in, out);
	return 0;
}


Measured memory_bytes: 3200