#include <bits/stdc++.h>
#define pb push_back
#define INF 0x3f3f3f3f
#define R read()
#define ll long long
#define N 100005
#define B 340
using namespace std;
inline int read(){
int x=0;char c=getchar();
while(c<'0'||c>'9') c=getchar();
while(c>='0'&&c<='9') x=x10+c-'0',c=getchar();
return x;
}
int T,k,n,m,s[N],b[N2],c[N2],wl[N],wr[N],ans;
int st[N],L,lp[N],rp[N];
char qc;
bool a[N2];
void work(int l,int r){
int cnt=0,ml1=0,ml2=0,mr1=0,mr2=0;
for(int i=1;i<=k;i++){
wl[i]=wr[i]=0;
for(int p=s[i];p<s[i+1];p++){
if(b[pn+r]-b[pn+l-1]0) wl[i];
else break;
}
for(int p=s[i+1]-1;p>=s[i];p--){
if(b[pn+r]-b[pn+l-1]==0) wr[i];
else break;
}
if(wl[i]s[i+1]-s[i]&&wl[i]wr[i]) cnt+=s[i+1]-s[i];
else{
if(wl[i]>=wl[ml2]){
if(wl[i]>=wl[ml1]) ml2=ml1,ml1=i;
else ml2=i;
}
if(wr[i]>=wr[mr2]){
if(wr[i]>=wr[mr1]) mr2=mr1,mr1=i;
else mr2=i;
}
}
}
// printf("%d %d: \n",l,r);
// for(int i=1;i<=k;i++)
// printf("%d %d\n",wl[i],wr[i]);
// printf("%d %d %d %d %d res=%d\n",cnt,ml1,ml2,mr1,mr2,(cnt+(ml1mr1?max(wl[ml1]+wr[mr2],wr[mr1]+wl[ml2]):wl[ml1]+wr[mr1]))*(r-l+1));
ans=max(ans,(cnt+(ml1mr1?max(wl[ml1]+wr[mr2],wr[mr1]+wl[ml2]):wl[ml1]+wr[mr1]))(r-l+1));
}
int main(){
T=R;
while(T--){
k=R,n=R+1,m=1,ans=0;
memset(b,0,sizeof b);
memset(c,0,sizeof c);
for(int i=1;i<=k;i++){
s[i]=m,m+=R;
for(int j=1;j<n;j++){
for(int p=s[i];p<m;p++){
qc=getchar();
a[pn+j]=(qc'1');
}
getchar();
}
}
s[k+1]=m--;
for(int i=1;i<=m;i++){
for(int j=1;j<n;j++)
b[in+j]=b[in+j-1]+a[in+j];
}
for(int i=1;i<=m;i++){
for(int j=1;j<n;j++){
if(a[in+j]) c[in+j]=0;
else c[in+j]=c[in+j-1]+1;
}
}
for(int j=1;j<n;j++){
L=0;
for(int i=1;i<=m;i++){
while(L>0&&c[st[L]n+j]>c[in+j])
rp[st[L]]=i,L--;
st[++L]=i;
}
while(L>0) rp[st[L--]]=m+1;
for(int i=m;i;i--){
while(L>0&&c[st[L]n+j]>c[in+j])
lp[st[L]]=i,L--;
st[L]=i;
}
while(L>0) lp[st[L--]]=0;
for(int i=1;i<=m;i) ans=max(ans,c[in+j](rp[i]-lp[i]-1));
}
if(n<B){
for(int l=1;l<n;l++){
for(int r=l;r<n;r++)
work(l,r);
}
}else{
for(int i=1;i<=m;i++){
for(int j=1;j<n;j++){
if(!a[in+j])
work(j-c[i*n+j]+1,j);
}
}
}
printf("%d\n",ans);
}
return 0;
}
