#include<cstdio>
#include<algorithm> 
using namespace std;
int up[203],down[203],f[203][203],ip[203][203],jp[203][203];
int n,m;

int main()
{ 
    scanf("%d%d",&n,&m);
    for(int i=1;i<=n;i++)
    scanf("%d",&up[i]);
    for(int i=1;i<=m;i++)
    scanf("%d",&down[i]);
    
    for(int i=1;i<=n;i++){
        for(int j=2;j<=m;j++){
            if(down[j-1]==up[i]) jp[i][j]=j-1; 
            else jp[i][j]=jp[i][j-1];
        }
    }
    for(int i=2;i<=n;i++){
        for(int j=1;j<=n;j++){
            if(up[i-1]==down[j]) ip[i][j]=i-1; 
            else ip[i][j]=ip[i-1][j];
        }
    }
    
    for(int i=1;i<=n;i++)
    for(int j=1;j<=m;j++)
    {
        f[i][j]=max(f[i-1][j],f[i][j-1]);
        f[i][j]=max(f[i-1][j-1],f[i][j]);
        
        if(up[i]!=down[j])
        {   int x=ip[i][j],y=jp[i][j];
            if(x!=0&&y!=0)
            f[i][j]=max(f[i][j],f[x-1][y-1]+2);
        }
        
        
    }
    printf("%d",f[n][m]);
    
    return 0;
}