acgo

#include<cstdio>
#include<cstring>
#include<algorithm>
using namespace std;

const int N=100007;

int T;
int s,n,m,ans,w[N],st[N],en[N],sum[N],a[N],up[N];

int id(int x,int y){
	if(x<1||y<1)return 0;
	return (y-1)*n+x;
}
int get(int x1,int x2,int y1,int y2){
	return sum[id(x2,y2)]-sum[id(x1-1,y2)]-sum[id(x2,y1-1)]+sum[id(x1-1,y1-1)];
}

void calc(int l,int r){
	for(int i=1;i<=s;++i)for(int j=st[i],ret=0;j<=en[i];++j){
		if(get(l,r,j,j)==0)++ret;
		else ret=0;
		ans=max(ans,(r-l+1)*ret);
	}
	int L[2][2],R[2][2],mid=0;
	memset(L,0,sizeof(L));
	memset(R,0,sizeof(R));
	for(int i=1;i<=s;++i){
		int mxl=0,mxr=0;
		for(int j=st[i];j<=en[i];++j)if(get(l,r,j,j)==0)++mxl;else break;
		for(int j=en[i];j>=st[i];--j)if(get(l,r,j,j)==0)++mxr;else break;
		if(mxl==w[i])mid+=w[i];
		else{
			if(mxl>L[0][0])L[0][0]=mxl,L[0][1]=i;
			else if(mxl>L[1][0])L[1][0]=mxl,L[1][1]=i;
			if(mxr>R[0][0])R[0][0]=mxr,R[0][1]=i;
			else if(mxr>R[1][0])R[1][0]=mxr,R[1][1]=i;
		}
	}
	for(int p=0;p<2;++p)for(int q=0;q<2;++q)if(L[p][1]!=R[q][1])ans=max(ans,(r-l+1)*(mid+L[p][0]+R[q][0]));
	ans=max(ans,(r-l+1)*(mid+L[0][0]));
	ans=max(ans,(r-l+1)*(mid+R[0][0]));
}

int main(){
	scanf("%d",&T);
	while(T--){
		m=ans=0;
		scanf("%d%d",&s,&n);
		memset(w,0,sizeof(w));
		memset(st,0,sizeof(st));
		memset(en,0,sizeof(en));
		memset(sum,0,sizeof(sum));
		memset(a,0,sizeof(a));
		memset(up,0,sizeof(up));
		for(int i=1;i<=s;++i){
			scanf("%d",&w[i]);
			st[i]=m+1;
			for(int j=1;j<=n;++j)for(int k=1;k<=w[i];++k){
				char c;scanf(" %c",&c);
				a[id(j,m+k)]=c-'0';
			}
			m+=w[i],en[i]=m;
		}
		for(int i=1;i<=n;++i)for(int j=1;j<=m;++j)sum[id(i,j)]=sum[id(i-1,j)]+sum[id(i,j-1)]-sum[id(i-1,j-1)]+a[id(i,j)];
		for(int j=1;j<=m;++j)
			for(int i=1,lst=0;i<=n+1;++i)
				if(i>n||a[id(i,j)]){
					for(int k=lst+1;k<=i-1;++k)up[id(k,j)]=i-1;
					lst=i;
				}
		if(n<m)for(int i=1;i<=n;++i)for(int j=i;j<=n;++j)calc(i,j);
		else for(int i=1;i<=n;++i)for(int j=1;j<=m;++j)calc(i,up[id(i,j)]);
		printf("%d\n",ans);
	}
	return 0;
}

//无