Common Subsequence

#include <bits/stdc++.h>
using namespace std;
#define PB push_back
#define ZERO (1e-10)
#define INF int(1e9+1)
#define CL(A,I) (memset(A,I,sizeof(A)))
#define DEB printf("DEB!\n");
#define D(X) cout<<"  "<<#X": "<<X<<endl;
#define EQ(A,B) (A+ZERO>B&&A-ZERO<B)
typedef long long ll;
typedef pair<ll,ll> pll;
typedef vector<int> vi;
typedef pair<int,int> ii;
typedef vector<ii> vii;
#define IN(n) int n;scanf("%d",&n);
#define FOR(i, m, n) for (int i(m); i < n; i++)
#define F(n) FOR(i,0,n)
#define FF(n) FOR(j,0,n)
#define FT(m, n) FOR(k, m, n)
#define aa first
#define bb second
void ga(int N,int *A){F(N)scanf("%d",A+i);}
#define MOD 1000000007
#define MX 2048
int dp[MX][MX][2][2],N,M,A[MX],B[MX];
int dyn(int a,int b,bool x,bool y){
    if(a==N||b==M)return !x&&!y;
    int&v=dp[a][b][x][y];
    if(~v)return v;
    v=0;
    if(A[a]==B[b])v=dyn(a+1,b+1,0,0);
    if(!x&&!y)v=(v+dyn(a+1,b+1,0,0))%MOD;
    if(x)v=(v+dyn(a,b+1,1,0))%MOD;
    if(y)v=(v+dyn(a+1,b,0,1))%MOD;
    if(!x&&!y)v=(v+ll(dyn(a+1,b,0,1))+dyn(a,b+1,1,0))%MOD;
    return v;
}
int main(void){
    scanf("%d%d",&N,&M),ga(N,A),ga(M,B),CL(dp,-1);
    printf("%d\n",dyn(0,0,0,0));
    return 0;
}
#include <bits/stdc++.h>
using namespace std;
#define PB push_back
#define ZERO (1e-10)
#define INF int(1e9+1)
#define CL(A,I) (memset(A,I,sizeof(A)))
#define DEB printf("DEB!\n");
#define D(X) cout<<"  "<<#X": "<<X<<endl;
#define EQ(A,B) (A+ZERO>B&&A-ZERO<B)
typedef long long ll;
typedef pair<ll,ll> pll;
typedef vector<int> vi;
typedef pair<int,int> ii;
typedef vector<ii> vii;
#define IN(n) int n;scanf("%d",&n);
#define FOR(i, m, n) for (int i(m); i < n; i++)
#define F(n) FOR(i,0,n)
#define FF(n) FOR(j,0,n)
#define FT(m, n) FOR(k, m, n)
#define aa first
#define bb second
void ga(int N,int *A){F(N)scanf("%d",A+i);}
#define MOD 1000000007
#define MX 2048
int dp[MX][MX][2][2],N,M,A[MX],B[MX];
int dyn(int a,int b,bool x,bool y){
    if(a==N||b==M)return !x&&!y;
    int&v=dp[a][b][x][y];
    if(~v)return v;
    v=0;
    if(A[a]==B[b])v=dyn(a+1,b+1,0,0);
    if(!x&&!y)v=(v+dyn(a+1,b+1,0,0))%MOD;
    if(x)v=(v+dyn(a,b+1,1,0))%MOD;
    if(y)v=(v+dyn(a+1,b,0,1))%MOD;
    if(!x&&!y)v=(v+ll(dyn(a+1,b,0,1))+dyn(a,b+1,1,0))%MOD;
    return v;
}
int main(void){
    scanf("%d%d",&N,&M),ga(N,A),ga(M,B),CL(dp,-1);
    printf("%d\n",dyn(0,0,0,0));
    return 0;
}