#include<cstdio>
#include<cctype>
#include<algorithm>
#define gc() (p1==p2&&(p2=(p1=buf)+fread(buf,1,1<<20,stdin),p1==p2)?EOF:*p1++)
using namespace std;
char buf[1<<20],*p1=buf,*p2=buf;
template<typename type>
inline void read(type &x)
{
    x=0;
    bool flag=0;char ch=gc();
    while(!isdigit(ch)) flag=ch=='-',ch=gc();
    while(isdigit(ch)) x=(x<<1)+(x<<3)+(ch^48),ch=gc();
    flag?x=-x:0;
}
const int MAXN=1e5+100;
int T,n,m,a[MAXN],b[MAXN];
int ans;
int main()
{
    read(T);
    while(T--)
    {
        ans=0;
        read(n),read(m);
        for(int i=1;i<=n;++i) read(a[i]);
        for(int i=1;i<=m;++i) read(b[i]);
        sort(a+1,a+n+1);
        sort(b+1,b+m+1);
        b[0]=-1,b[m+1]=0x3f3f3f3f;
        for(int i=1;i<=m+1;++i)
        {
            int l=upper_bound(a+1,a+n+1,b[i-1])-a,r=lower_bound(a+1,a+n+1,b[i])-a;
            ans=max(ans,r-l);
        }
        if(!ans) puts("Impossible");
        else printf("%d\n",ans);
        
    }
    return 0;
}