#include<bits/stdc++.h>
using namespace std;
int main(){
int t;
cin>>t;
while(t--){
int n,m;
cin>>n>>m;
int dish[n][2];//1st index is for day and 2nd index is for tastiness
int t1, t2, d1, d2;
t1=t2=d1=d2=-1;
for(int i=0;i<n;i++){
cin>>dish[i][0]>>dish[i][1];
if(dish[i][1]>=t1){
if(dish[i][0]!=d1){
t2=t1;
d2=d1;
d1=dish[i][0];
t1=dish[i][1];
}
else{
d1=dish[i][0];
t1=dish[i][1];
}
}
else if(dish[i][1]>t2 && dish[i][0]!=d1){
t2=dish[i][1];
d2=dish[i][0];
}
}
cout<<t1+t2<<endl;
}
return 0;
}
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