#pragma GCC optimize("Ofast")
#include<bits/stdc++.h>

using namespace std;
using Int = long long;
typedef pair<int,int> Pi; typedef pair<Int,Int> Pl;
constexpr int mod = 1e9+7;
constexpr int INF32 = numeric_limits<int>::max();
constexpr Int INF64 = numeric_limits<Int>::max();
#define END {cout<<ans<<'\n'; return 0;}
#define ALL(v) (v).begin(),(v).end()
#define fi first
#define se second
#define mp make_pair
#define eb emplace_back
#define Pr(t) priority_queue<t>
#define gPr(t) priority_queue<t,vector<t>,greater<t>>
#define V(t) vector<t>
#define rer(i,l,r) for(int i=(l); i<(r); ++i)
#define rep(i,n) rer(i,0,n)
#define gnr(i,l,r) for(int i=(r)-1; i>=(l); --i)
#define pri(a) cout<<(a)<<'\n'
#define pri2(a,n) {rep(i,n-1)cout<<a[i]<<' '; if(n)cout<<a[n-1]<<'\n';}
#define prip(p) cout<<(p).fi<<' '<<(p).se<<'\n'
template<class T> inline bool cmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; }
template<class T> inline bool cmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; }

Int n,m,_,x,y,q;
string s,sb;
bool ok;
char cf,cb;

template<int MOD>
struct ModInt {
	static const int Mod = MOD;
	unsigned x;
	ModInt() : x(0) {}
	ModInt(signed sig) { int sigt = sig % MOD; if(sigt < 0) sigt += MOD; x = sigt; }
	ModInt(signed long long sig) { int sigt = sig % MOD; if(sigt < 0) sigt += MOD; x = sigt; }
	int get() const { return (int)x; }

	ModInt &operator+=(ModInt that) { if((x += that.x) >= MOD) x -= MOD; return *this; }
	ModInt &operator-=(ModInt that) { if((x += MOD - that.x) >= MOD) x -= MOD; return *this; }
	ModInt &operator*=(ModInt that) { x = (unsigned long long)x * that.x % MOD; return *this; }
	ModInt &operator/=(ModInt that) { return *this *= that.inverse(); }
  ModInt &operator%=(ModInt that) { x %= that.x; return *this; }

	ModInt operator+(ModInt that) const { return ModInt(*this) += that; }
	ModInt operator-(ModInt that) const { return ModInt(*this) -= that; }
	ModInt operator*(ModInt that) const { return ModInt(*this) *= that; }
	ModInt operator/(ModInt that) const { return ModInt(*this) /= that; }
  ModInt operator%(ModInt that) const { return ModInt(*this) %= that; }

	ModInt inverse() const {
		signed a = x, b = MOD, u = 1, v = 0;
		while(b) {
			signed t = a / b;
			a -= t * b; std::swap(a, b);
			u -= t * v; std::swap(u, v);
		}
		if(u < 0) u += Mod;
		ModInt res; res.x = (unsigned)u;
		return res;
	}

	bool operator==(ModInt that) const { return x == that.x; }
	bool operator!=(ModInt that) const { return x != that.x; }
	ModInt operator-() const { ModInt t; t.x = x == 0 ? 0 : Mod - x; return t; }

  friend ostream &operator<<(ostream &os, const ModInt &p) {
    return os << p.x;
  }

  friend istream &operator>>(istream &is, ModInt &a) {
    int t;
    is >> t;
    a = ModInt< mod >(t);
    return (is);
  }
};
template<int MOD> ModInt<MOD> operator^(ModInt<MOD> a, unsigned long long k) {
	ModInt<MOD> r = 1;
	while(k) {
		if(k & 1) r *= a;
		a *= a;
		k >>= 1;
	}
	return r;
}

typedef ModInt<mod> mint;

vector<mint> fact, factinv;

void COMinit(int N) {
	N = min(N, mint::Mod - 1);
	fact.resize(N + 1); factinv.resize(N + 1);
	fact[0] = 1;
	for (int i = 1; i <= N; i++) fact[i] = fact[i - 1] * i;
	factinv[N] = fact[N].inverse();
	for(int i = N; i >= 1; i --) factinv[i - 1] = factinv[i] * i;
}

mint C(int n, int r) {
	if(n >= mint::Mod)
		return C(n % mint::Mod, r % mint::Mod) * C(n / mint::Mod, r / mint::Mod);
	return r > n ? 0 : fact[n] * factinv[n - r] * factinv[r];
}

int main(){
  cin.tie(nullptr); ios::sync_with_stdio(0);
  //cout<<fixed<<setprecision(20);

  cin>>n>>m; if(abs(n-m)>1){pri(0); return 0;}
  COMinit(100000);
  mint ans=fact[n]*fact[m];
  if(n==m)ans*=2;
  END
}

Measured memory_bytes: 3944