#include <bits/stdc++.h>
using namespace std;
#define gc getchar_unlocked
#define fo(i, n) for (int i = 0; i < n; i++)
#define rfo(i, n) for (int i = n - 1; i >= 0; i--)
#define REP(i, a, b) for (int i = a; i < b; i++)
#define RREP(i, a, b) for (int i = a; i >= b; i--)
#define ll long long
#define si(x) scanf("%d", &x)
#define sl(x) scanf("%lld", &x)
#define ss(s) scanf("%s", s)
#define pi(x) printf("%d\n", x)
#define pl(x) printf("%lld\n", x)
#define ps(s) printf("%s\n", s)
#define deb(x) cout << #x << "=" << x << endl
#define deb2(x, y) cout << #x << "=" << x << "," << #y << "=" << y << endl
#define deb3(x, y, z) cout << #x << "=" << x << "," << #y << "=" << y << "," << #z << "=" << z << endl
#define pb push_back
#define mp make_pair
#define F first
#define S second
#define all(x) x.begin(), x.end()
#define clr(x) memset(x, 0, sizeof(x))
#define sortall(x) sort(all(x))
#define tr(it, a) for (auto it = a.begin(); it != a.end(); it++)
#define PI 3.1415926535897932384626
typedef pair<int, int> pii;
typedef pair<ll, ll> pl;
typedef vector<int> vi;
typedef vector<ll> vl;
typedef vector<pii> vpii;
typedef vector<pl> vpl;
typedef vector<vi> vvi;
typedef vector<vl> vvl;
int mpow(int base, int exp);
void dfs(int u, int par);
const int mod = 1'000'000'007;
const int N = 3000 + 100, M = N;
vi g[N];
ll dp[N][N], ans[N];
void solve()
{
int h, w;
cin >> h >> w;
// dp[i][j] i free rows, j free coloumns
ll ans = 0;
fo(i, h + 1)
{
fo(j, w + 1)
{
if (i == 0 || j == 0)
dp[i][j] = 1;
else
{
// place nothing
dp[i][j] += dp[i - 1][j];
// place any one tent
dp[i][j] += (4 * j * dp[i - 1][j - 1]);
// place < >
if (j >= 2)
dp[i][j] += ((((j * (j - 1)) / 2)) * dp[i - 1][j - 2]);
// place up down
if (i >= 2)
dp[i][j] += (((j * (i - 1))) * (dp[i - 2][j - 1]));
dp[i][j] %= mod;
}
}
}
ans = dp[h][w] - 1;
ans %= mod;
ans += mod;
ans %= mod;
cout << ans << '\n';
return;
}
int main()
{
ios_base::sync_with_stdio(0), cin.tie(0), cout.tie(0);
srand(chrono::high_resolution_clock::now().time_since_epoch().count());
int t = 1;
int cs = 0;
while (t - cs)
{
solve();
cs++;
}
return 0;
}
int mpow(int base, int exp)
{
base %= mod;
int result = 1;
while (exp > 0)
{
if (exp & 1)
result = ((ll)result * base) % mod;
base = ((ll)base * base) % mod;
exp >>= 1;
}
return result;
}
void ipgraph(int n, int m)
{
int u, v;
while (m--)
{
cin >> u >> v;
u--, v--;
g[u].pb(v);
g[v].pb(u);
}
}
void dfs(int u, int par)
{
for (int v : g[u])
{
if (v == par)
continue;
dfs(v, u);
}
}
