#include <cstdio>
#include <cstring>
#include <iostream>
#include <string>
#include <cmath>
#include <bitset>
#include <vector>
#include <map>
#include <set>
#include <queue>
#include <deque>
#include <algorithm>
#include <complex>
#include <unordered_map>
#include <unordered_set>
#include <random>
#include <cassert>
#include <fstream>
#include <utility>
#include <functional>
#include <time.h>
#include <stack>
#include <array>
#include <list>
#include <atcoder/all>
#define popcount __builtin_popcount
using namespace std;
using namespace atcoder;
typedef long long ll;
typedef pair<int, int> P;

int main()
{
    int t; cin>>t;
    while(t--){
        int n, m;
        ll k;
        cin>>n>>m>>k;
        vector<ll> c(n), s(n);
        ll ans=0;
        for(int i=0; i<m; i++){
            int x;
            ll y;
            cin>>x>>y;
            x--;
            c[x]++;
            s[x]+=y;
            ans+=y*y;
        }
        ll l=-2e18, r=1e15;
        while(r-l>1){
            ll m=(l+r)/2;
            ll cnt=0;
            for(int i=0; i<n; i++){
                if(c[i]==0){
                    if(m>=0) cnt=1e18;
                }else{
                    if(m+2*s[i]+c[i]>0) cnt+=(m+2*s[i]+c[i])/(2*c[i]);
                }
            }
            if(cnt>=k) r=m;
            else l=m;
        }
        ll cnt1=0;
        for(int i=0; i<n; i++){
            if(c[i]==0) continue;
            if(r-1+2*s[i]+c[i]>0){
                ll x=(r-1+2*s[i]+c[i])/(2*c[i]);
                cnt1+=x;
                ans+=x*x*c[i]-2*s[i]*x;
            }
        }
        ans+=(k-cnt1)*r;
        cout<<ans<<endl;
    }
    return 0;
}