#include <bits/stdc++.h>
#pragma GCC optimize("Ofast")
#define _GLIBCXX_DEBUG
using namespace std;
using std::cout;
using std::cin;
using std::endl;
using ll=long long;
using ld=long double;
ll ILL=1167167167167167167;
const int INF=2100000000;
const ll mod=1e9+7;
#define rep(i,a) for (int i=0;i<a;i++)
template<class T> using _pq = priority_queue<T, vector<T>, greater<T>>;
template<class T> ll LB(vector<T> &v,T a){return lower_bound(v.begin(),v.end(),a)-v.begin();}
template<class T> ll UB(vector<T> &v,T a){return upper_bound(v.begin(),v.end(),a)-v.begin();}
template<class T> bool chmin(T &a,const T &b){if(a>b){a=b;return 1;}else return 0;}
template<class T> bool chmax(T &a,const T &b){if(a<b){a=b;return 1;}else return 0;}
template<class T> void So(vector<T> &v) {sort(v.begin(),v.end());}
template<class T> void Sore(vector<T> &v) {sort(v.begin(),v.end(),[](T x,T y){return x>y;});}
void yneos(bool a){if(a) cout<<"Yes\n"; else cout<<"No\n";}



void solve();
//  rainy ~ 雨に打たれて ~
int main() {
	ios::sync_with_stdio(false);
	cin.tie(nullptr);
	
	int t=1;
	cin>>t;
	rep(i,t) solve();
}

void solve(){
    ll N,M,K;
    cin>>N>>M>>K;
    vector<vector<ll>> G(N);
    rep(i,M){
        ll x,y;
        cin>>x>>y;
        G[x-1].push_back(y);
    }
    int J=0;
    ll bestsum=0;
    vector<ll> best(N),sum(N),sum2(N),size(N);
    rep(i,N){
        size[i]=G[i].size();
        if(size[i]==0){
            J=1;
            continue;
        }
        for(auto x:G[i]){
            sum[i]+=x;
            sum2[i]+=x*x;
        }
        best[i]=(2*sum[i]+size[i]-1)/(2*size[i]);
        bestsum+=best[i];
    }
    if(bestsum<=K){
        if(J){
            ll ans=0;
            rep(i,N){
                ans+=best[i]*(best[i]*size[i]-2*sum[i])+sum2[i];
            }
            cout<<ans<<"\n";
            return ;
        }
        ll l=-1,r=ILL;
        while(r-l>1){
            ll med=(r+l)/2;
            ll tmp=0;
            rep(i,N){
                if(tmp>K) break;
                if(size[i]) tmp+=(med+2*sum[i]-size[i])/(2*size[i])+1;
            }
            if(tmp>K) r=med;
            else l=med;
        }
        ll ans=0;
        ll c=0;
        rep(i,N){
            ll b=(l+2*sum[i]-size[i])/(2*size[i])+1;
            c+=b;
            ans+=b*(b*size[i]-2*sum[i])+sum2[i];
        }
        cout<<ans+r*(K-c)<<"\n";
    }else{
        ll l=-ILL,r=1;
        while(r-l>1){
            ll med=(r+l)/2;
            ll tmp=0;
            rep(i,N){
                if(tmp>K) break;
                if(size[i]) tmp+=max(0ll,(2*sum[i]+med+size[i]-1)/(2*size[i]));
            }
            if(tmp>K) r=med;
            else l=med;
        }
        ll ans=0;
        ll c=0;
        rep(i,N){
            if(size[i]==0) continue;
            ll b=max(0ll,(r+2*sum[i]+size[i]-1)/(2*size[i]));
            c+=b;
            ans+=b*(b*size[i]-2*sum[i])+sum2[i];
        }
        cout<<ans-l*(c-K)<<"\n";
    }
}