#include <iostream>
#include <cstring>
#include <algorithm>
#include <bits/stdc++.h>
using namespace std;
bool book(int a[],int n,int m,int mid){
int pag = 0,curr = 1;
for(int i=0;i<n;i++){
if(pag+a[i]>mid){
pag = a[i];
curr++;
if(curr>m){
return false;
}
}
else{
pag+=a[i];
}
}
return true;
}
int main(){
int t;
cin >> t;
while(t--){
int n,m;
cin >> n>>m;
int a[n];
int end = 0;
for(int i=0;i<n;i++){
cin >> a[i];
end +=a[i];
}
if(n<m){
cout<<-1<<"\n";
}
else{
int sta = 0,ans = INT_MAX;
while(sta<=end){
int mid = (sta+end)/2;
//cout<<mid<<"\n";
bool boo = book(a,n,m,mid);
if(boo){
//cout<<mid<<"\n";
ans = min(ans,mid);
//cout<<ans<<" "<<sta<<" "<<end<<" "<<mid<<" "<<"a"<<"\n";
end = mid-1;
}
else{
//cout<<mid<<"\n";
//cout<<ans<<" "<<sta<<" "<<end<<" "<<mid<<" "<<"b"<<"\n";
sta = mid+1;
}
}
cout<<ans<<"\n";
}
}
}
