#include <cstdio>
#include <iostream>
#include <algorithm>
#include <cstring>
#include <vector>
using namespace std;
#define fi first
#define sc second
#define mkp make_pair
#define pii pair<int,int>
typedef long long ll;
const int N=4005,oo=1e9,mod=1e9+7;
inline int read() {
    int x=0,flag=0;char ch=getchar();
    while(ch<'0'||ch>'9') {flag|=(ch=='-');ch=getchar();}
    while('0'<=ch&&ch<='9') {x=(x<<3)+(x<<1)+ch-'0';ch=getchar();}
    return flag?-x:x;
}
inline int mx(int x,int y) {return x>y?x:y;}
inline int mn(int x,int y) {return x<y?x:y;}
inline void swp(int &x,int &y) {x^=y^=x^=y;}
inline int as(int x) {return x>0?x:-x;}

int n,m,C[N][N],S[N][N];
inline void prep() {
    int L=mx(n,m);
    C[0][0]=S[0][0]=1;
    C[1][0]=C[1][1]=1;S[1][0]=S[1][1]=1;
    for(int i=2;i<=L;++i) {
        C[i][0]=C[i][i]=1;
        for(int j=1;j<i;++j)
            C[i][j]=(C[i-1][j-1]+C[i-1][j])%mod;
        for(int j=0;j<=i;++j)
            S[i][j]=(S[i-2][j]+C[i][j])%mod;
    }
}
inline void solve_odd() {
    int ans=0,L=n/2;
    for(int i=0;i<=L;++i)
        for(int j=0;j<=L;++j) {
            if(i==0&&j==0) continue;
            ans=(ans+1ll*C[n][i]*C[n-i][j]%mod*S[m-1][i+j-1])%mod;
            if(i<=j) {
                if(m-n-i+j<0) continue;
                ans=(ans+1ll*C[n][i]*C[n-i][j]%mod*S[m-n-i+j+(i+j-1)][i+j-1])%mod;
            } else {
                if(m-n-j+i<0) continue;
                ans=(ans+1ll*C[n][i]*C[n-i][j]%mod*S[m-n-j+i+(i+j-1)][i+j-1])%mod;
            }
        }
    if(m%2==0||m>=n) ans=(ans+1)%mod;
    printf("%d\n",ans);
}
inline void solve_even() {
    int ans=0,L=n/2;
    for(int i=0;i<=L;++i)
        for(int j=0;j<L;++j) {
            if(i==0&&j==0) continue;
            ans=(ans+1ll*C[n][i]*C[n-i][j]%mod*S[m-1][i+j-1])%mod;
        }
    if(m%2==0) ans=(ans+1)%mod;
    printf("%d\n",ans);
}
int main() {
    n=read();m=read();
    prep();
    if(n&1) solve_odd();
    else solve_even();
    return 0;
}