#define _USE_MATH_DEFINES
#include "bits/stdc++.h"
using namespace std;
#define FOR(i,j,k) for(int (i)=(j);(i)<(int)(k);++(i))
#define rep(i,j) FOR(i,0,j)
#define each(x,y) for(auto &(x):(y))
#define mp make_pair
#define MT make_tuple
#define all(x) (x).begin(),(x).end()
#define debug(x) cout<<#x<<": "<<(x)<<endl
#define smax(x,y) (x)=max((x),(y))
#define smin(x,y) (x)=min((x),(y))
#define MEM(x,y) memset((x),(y),sizeof (x))
#define sz(x) (int)(x).size()
#define RT return
using ll = long long;
using pii = pair<int, int>;
using vi = vector<int>;
using vll = vector<ll>;

void solve() {
    int T;
    cin >> T;
    while (T--) {
        int N, M, K;
        cin >> N >> M >> K;
        vll S(N), A(N), B(N);
        rep(i, M) {
            int x, y;
            cin >> x >> y;
            --x;
            S[x]++;
            A[x] += y;
            B[x] += (ll)y * y;
        }

        ll LIM = (ll)1e18;
        ll ng = LIM + 10, ok = -(ll)1e15;
        bool zero = find(all(S), 0ll) != S.end() ? true : false;
        if (zero)ng = 1;

        auto f = [&](ll z) {
            ll sm = 0, k = 0, just = 0;
            rep(i, N) {
                if (!S[i])continue;
                ll x = max((z + S[i] + 2 * A[i]) / (2 * S[i]), 0ll);
                k += x;
                sm += S[i] * x * x - 2 * A[i] * x + B[i];

                ll w = 2 * S[i] * x - S[i] - 2 * A[i];
                if (w == z && x > 0) {
                    just++;
                    k--;
                    sm -= w;
                }
                
                if (sm > LIM) {
                    k = K + 1;
                    break;
                }
                if (k > K)break;
            }
            if (k < K && just) {
                ll a = min(K - k, just);
                k += a;
                sm += a * z;
            } else if (just && K == k) {
                k++;
            }
            if (z == 0 && zero && k < K)k = K;
            return pair<ll, ll>(sm, k);
        };

        while (ng - ok > 1) {
            ll z = (ok + ng) / 2;
            ll sm, k;
            tie(sm, k) = f(z);
            (k <= K ? ok : ng) = z;
        }
        cout << f(ok).first << endl;
    }
}

int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout << fixed << setprecision(15);
    solve();
    return 0;
}