#include <stdio.h>
#include <string.h>
#include <math.h>
#include <stdlib.h>

int main() {

int q,n,i=0,chk1=1,chk2=1;
scanf("%d",&q);
scanf("%d",&n);

int x[n],y[n];
while(chk1<=q){    
while(n>i){
    scanf("%d %d",&x[i],&y[i]);
    i++;    
}
i=0;
for(int j=1;j<n;j++){
    if(x[i]!=x[j] && y[i]!=y[j]){
        printf("NO\n");
        chk2=0;
        break;
}
}
if(chk2!=0)    
printf("YES\n");
chk1++;
chk2=1;
i=0;
}
return 0;
}