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#include<cstdio>
#include<cstring>
#include<algorithm>
#include<iostream>
#include<queue>
#include<map>
#include<stack>
#include<cmath>
#include<set>
#include<bitset>
#include<complex>
#include<cstdlib>
#include<assert.h>
#define inc(i,l,r) for(int i=l;i<=r;i++)
#define dec(i,l,r) for(int i=l;i>=r;i--)
#define link(x) for(edge *j=h[x];j;j=j->next)
#define mem(a) memset(a,0,sizeof(a))
#define ll long long
#define mid (x+y>>1)
#define eps 1e-8
#define succ(x) (1ll<<(x))
#define lowbit(x) (x&(-x))
#define sqr(x) ((x)*(x))
#define NM 55
#define nm 10005
using namespace std;
const double pi=acos(-1);
const int inf=998244353;
ll read(){
ll x=0,f=1;char ch=getchar();
while(!isdigit(ch)){if(ch=='-')f=-1;ch=getchar();}
while(isdigit(ch))x=x*10+ch-'0',ch=getchar();
return f*x;
}
struct edge{int t;edge*next;}e[nm],*h[NM],*o=e;
void add(int x,int y){o->t=y;o->next=h[x];h[x]=o++;}
int n,m,_p,f[NM],tot,c[NM];
bool a[NM][NM];
int find(int x){return f[x]==x?x:f[x]=find(f[x]);}
char str[NM][NM],_str[NM][NM];
bool cmp(char*x,char*y){
int s=0;
inc(i,0,m-1)if(x[i]==y[i])s++;
return s<_p;
}
bool v[NM];
queue<int>q;
int d[NM];
vector<int>cnt[2],ans;
vector<int>vec[NM];
void solve(){
mem(v);mem(d);mem(h);o=e;
ans.clear();
while(!q.empty())q.pop();
n=read();m=read();_p=read();
inc(i,1,n){
scanf("%s",str[i]);
reverse_copy(str[i],str[i]+strlen(str[i]),_str[i]);
}
inc(i,1,n)f[i]=i;
inc(i,1,n)inc(j,i+1,n){
if(cmp(str[i],str[j])){
if(cmp(str[i],_str[j])){printf("-1\n");return;}
a[i][j]=a[j][i]=true;
}else{
a[i][j]=a[j][i]=false;
if(cmp(str[i],_str[j]))
f[find(i)]=find(j);
}
}
tot=0;
inc(i,1,n)if(find(i)==i)c[i]=++tot;
inc(i,1,tot)vec[i].clear();
inc(i,1,n)vec[c[find(i)]].push_back(i);
inc(i,1,tot)for(auto&j:vec[i])for(auto&k:vec[i])if(a[j][k]){printf("-1\n");return;}
inc(i,1,n)inc(j,1,n)if(a[i][j]&&find(i)!=find(j)){
add(c[find(i)],c[find(j)]);
}
inc(i,1,tot)if(!v[i]){
v[i]++;cnt[0].clear();cnt[1].clear();
q.push(i);
while(!q.empty()){
int t=q.front();q.pop();
for(auto&j:vec[t])cnt[d[t]].push_back(j);
link(t)if(!v[j->t]){
v[j->t]++;
d[j->t]=d[t]^1;
q.push(j->t);
}else if(d[j->t]==d[t]){printf("-1\n");return;}
}
if(cnt[0].size()<cnt[1].size())
for(auto&j:cnt[0])ans.push_back(j);
else
for(auto&j:cnt[1])ans.push_back(j);
}
printf("%d\n",(int)ans.size());
for(auto&j:ans)printf("%d ",j);putchar('\n');
}
int main(){
int _=read();while(_--)solve();
return 0;
}
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