import java.io.*; import java.util.*;
public class tents{
static class FastReader
{
BufferedReader br;
StringTokenizer st;
public FastReader()
{
br = new BufferedReader(new
InputStreamReader(System.in));
}
String next()
{
while (st == null || !st.hasMoreElements())
{
try
{
st = new StringTokenizer(br.readLine());
}
catch (IOException e)
{
e.printStackTrace();
}
}
return st.nextToken();
}
int nextInt()
{
return Integer.parseInt(next());
}
}
public static class Pair implements Comparable<Pair>{
int vtx; int val;
public Pair(int a, int b){
this.vtx=a; this.val=b;
}
public int compareTo(Pair other){
if(this.val<other.val)return -1;
if(this.val>other.val)return 1;
if(this.vtx<other.vtx)return -1;
return 1;
}
}
static int MOD=1000000007;
static int[] rk, p,siz;
public static void main(String[] args){
FastReader br=new FastReader();
int N=br.nextInt(); int M=br.nextInt();
long[][] dp=new long[N+1][M+1];
for (int i = 0; i <=N; i++) {
dp[i][0]=1;
}
for (int i = 1; i <=M; i++) {
dp[0][i]=1;
}
for (int x = 1; x <=N; x++) {
for (int y = 1; y <=M; y++) {//x rows, y columns
dp[x][y]=dp[x][y-1];
if(x>=2){dp[x][y]+=(x*(x-1)/2)*dp[x-2][y-1]; dp[x][y]%=MOD;}
dp[x][y]+=dp[x-1][y-1]*4*x; dp[x][y]%=MOD;
if(y>=2)dp[x][y]+=dp[x-1][y-2]*x*(y-1); dp[x][y]%=MOD;
}
}
System.out.println(dp[N][M]-1);
}
public static int find(int x, int[] p){
if(p[x]==x)return x;
int ans=find(p[x],p); p[x]=ans; return ans;
}
public static void merge(int a, int b) {
if(rk[a]<rk[b]) {
p[a]=b; siz[b]+=siz[a];
}else if(rk[a]==rk[b]) {
p[a]=b; rk[b]++;siz[b]+=siz[a];
}else {
p[b]=a; siz[a]+=siz[b];
}
}
}
//Debugging:
//Are you sure your algorithm is correct?
//Bounds: long
//Special cases: n=0,1?
//Make sure you remove your debugging code before you submit!
