#include<bits/stdc++.h>
using namespace std;

#define reg register
typedef long long ll;
#define rep(i,a,b) for(reg int i=a,i##end=b;i<=i##end;++i)
#define drep(i,a,b) for(reg int i=a,i##end=b;i>=i##end;--i)

char IO;
int rd(){
    int s=0,f=0;
    while(!isdigit(IO=getchar())) if(IO=='-') f=1;
    do s=(s<<1)+(s<<3)+(IO^'0');
    while(isdigit(IO=getchar()));
    return f?-s:s;
}

const int N=110;

int n,m;
int a[N];

char s1[N],s2[N];
int can[N][N];


int main(){
    rep(kase,1,rd()) {
        n=rd();m=rd();
        rep(i,1,m) rep(j,1,m) can[i][j]=1;
        rep(t,1,n) {
            scanf("%s%s",s1+1,s2+1);
            rep(i,1,m) rep(j,1,m) if(s1[i]!=s2[j]) can[i][j]=0;
        }
        int fl=1;
        rep(i,1,m) {
            a[i]=-1;
            rep(j,1,m) if(can[i][j]) {
                a[i]=j;
                break;
            }
            if(a[i]==-1) {
                fl=0;
                break;
            }
            rep(j,1,m) can[j][a[i]]=0;
        }
        if(fl) {
            rep(i,1,m) printf("%d%c",a[i],i==m?'\n':' ');
        } else puts("-1");
    }
}