using System;
using System.Collections.Generic;
using System.Linq;
using System.IO;
using System.Threading;
using System.Text;
using System.Text.RegularExpressions;
using System.Diagnostics;
using static util;
using P = pair<int, int>;

class Program {
    static void Main(string[] args) {
        var sw = new StreamWriter(Console.OpenStandardOutput()) { AutoFlush = false };
        var solver = new Solver(sw);
        // var t = new Thread(solver.solve, 1 << 28); // 256 MB
        // t.Start();
        // t.Join();
        solver.solve();
        sw.Flush();
    }
}

class Solver {
    StreamWriter sw;
    Scan sc;
    void Prt(string a) => sw.WriteLine(a);
    void Prt<T>(IEnumerable<T> a) => Prt(string.Join(" ", a));
    void Prt(params object[] a) => Prt(string.Join(" ", a));
    public Solver(StreamWriter sw) {
        this.sw = sw;
        this.sc = new Scan();
    }

    public void solve() {
        long calc_cost(long[] f, long x) {
            return x * x * f[2] + x * f[1] + f[0];
        }

        int T = sc.Int;
        for (int _ = 0; _ < T; _++)
        {
            int n, m, k;
            sc.Multi(out n, out m, out k);
            // var lis = new List<long>[n];
            var f = new long[n][];
            for (int i = 0; i < n; i++)
            {
                f[i] = new long[3];
            }
            for (int i = 0; i < m; i++)
            {
                long x, y;
                sc.Multi(out x, out y);
                --x;
                f[x][0] += y * y;
                f[x][1] -= 2 * y;
                f[x][2]++;
            }
            bool emp = false;
            var cnt = new long[n];
            long cost = 0;
            for (int i = 0; i < n; i++)
            {
                if (f[i][2] == 0) {
                    emp = true;
                    continue;
                }
                long b = -f[i][1] / 2;
                long a = f[i][2];
                long q = b % a;
                long cc;
                if (q * 2 < b) {
                    cc = b / a;
                }
                else {
                    cc = b / a + 1;
                }
                cnt[i] = cc;
                cost += calc_cost(f[i], cc);
            }
            long sum = cnt.Sum();
            if (sum == k || sum < k && emp) {
                Prt(cost);
                continue;
            }
            if (sum > k) {
                long ng = -1, ok = M;
                while (ng + 1 < ok) {
                    long mid = (ng + ok) / 2;
                    long cc = 0;
                    for (int i = 0; i < n; i++)
                    {
                        if (f[i][2] == 0) continue;
                        long x = Math.Max((-mid - f[i][1] - f[i][2] + 2 * f[i][2] - 1) / (2 * f[i][2]), 0);
                        Assert(x <= cnt[i]);
                        cc += x;
                    }
                    if (cc <= k) {
                        ok = mid;
                    }
                    else {
                        ng = mid;
                    }
                }
                {
                    long cc = 0;
                    long ans = 0;
                    for (int i = 0; i < n; i++)
                    {
                        if (f[i][2] == 0) continue;
                        long x = Math.Max((-ok - f[i][1] - f[i][2] + 2 * f[i][2] - 1) / (2 * f[i][2]), 0);
                        Assert(x <= cnt[i]);
                        ans += calc_cost(f[i], x);
                        cc += x;
                    }
                    Assert(k >= cc);
                    ans -= (k - cc) * ok;
                    Prt(ans);
                }
            }
            else {
                long ng = -1, ok = M;
                while (ng + 1 < ok) {
                    long mid = (ng + ok) / 2;
                    long cc = 0;
                    for (int i = 0; i < n; i++)
                    {
                        if (f[i][2] == 0) continue;
                        long x = (mid - f[i][1] - f[i][2]) / (2 * f[i][2]);
                        Assert(x >= cnt[i]);
                        cc += x;
                    }
                    if (cc >= k) {
                        ok = mid;
                    }
                    else {
                        ng = mid;
                    }
                }
                {
                    long cc = 0;
                    long ans = 0;
                    for (int i = 0; i < n; i++)
                    {
                        if (f[i][2] == 0) continue;
                        long x = (ok - f[i][1] - f[i][2]) / (2 * f[i][2]);
                        Assert(x >= cnt[i]);
                        ans += calc_cost(f[i], x);
                        cc += x;
                    }
                    Assert(k <= cc);
                    ans -= (cc - k) * ok;
                    Prt(ans);
                }

            }


        }

    }
}

class pair<T, U> : IComparable<pair<T, U>> {
    public T v1;
    public U v2;
    public pair() : this(default(T), default(U)) {}
    public pair(T v1, U v2) { this.v1 = v1; this.v2 = v2; }
    public int CompareTo(pair<T, U> a) {
        int c = Comparer<T>.Default.Compare(v1, a.v1);
        return c != 0 ? c : Comparer<U>.Default.Compare(v2, a.v2);
    }
    public override string ToString() => $"{v1} {v2}";
    public void Deconstruct(out T a, out U b) { a = v1; b = v2; }
}
static class util {
    public static readonly int M = 1000000007;
    // public static readonly int M = 998244353;
    public static readonly long LM = 1L << 60;
    public static readonly double eps = 1e-11;
    public static void DBG(string a) => Console.Error.WriteLine(a);
    public static void DBG<T>(IEnumerable<T> a) => DBG(string.Join(" ", a));
    public static void DBG(params object[] a) => DBG(string.Join(" ", a));
    public static void Assert(params bool[] conds) {
        if (conds.Any(x => !x)) throw new Exception();
    }
    public static pair<T, U> make_pair<T, U>(T v1, U v2) => new pair<T, U>(v1, v2);
    public static int CompareList<T>(IList<T> a, IList<T> b) where T : IComparable<T> {
        for (int i = 0; i < a.Count && i < b.Count; i++)
            if (a[i].CompareTo(b[i]) != 0) return a[i].CompareTo(b[i]);
        return a.Count.CompareTo(b.Count);
    }
    public static bool inside(int i, int j, int h, int w) => i >= 0 && i < h && j >= 0 && j < w;
    public static readonly int[] dd = { 0, 1, 0, -1 };
    // static readonly string dstring = "RDLU";
    public static IEnumerable<P> adjacents(int i, int j) {
        for (int k = 0; k < 4; k++) yield return new P(i + dd[k], j + dd[k ^ 1]);
    }
    public static IEnumerable<P> adjacents(int i, int j, int h, int w) {
        for (int k = 0; k < 4; k++) if (inside(i + dd[k], j + dd[k ^ 1], h, w))
            yield return new P(i + dd[k], j + dd[k ^ 1]);
    }
    public static IEnumerable<P> adjacents(this P p) => adjacents(p.v1, p.v2);
    public static IEnumerable<P> adjacents(this P p, int h, int w) => adjacents(p.v1, p.v2, h, w);
    public static IEnumerable<int> all_subset(this int p) {
        for (int i = 0; ; i = i - p & p) {
            yield return i;
            if (i == p) break;
        }
    }
    public static Dictionary<T, int> compress<T>(this IEnumerable<T> a)
        => a.Distinct().OrderBy(v => v).Select((v, i) => new { v, i }).ToDictionary(p => p.v, p => p.i);
    public static Dictionary<T, int> compress<T>(params IEnumerable<T>[] a)
        => compress(a.SelectMany(x => x));
    public static T[] inv<T>(this Dictionary<T, int> dic) {
        var res = new T[dic.Count];
        foreach (var item in dic) res[item.Value] = item.Key;
        return res;
    }
    public static void swap<T>(ref T a, ref T b) where T : struct { var t = a; a = b; b = t; }
    public static void swap<T>(this IList<T> a, int i, int j) where T : struct {
        var t = a[i]; a[i] = a[j]; a[j] = t;
    }
    public static T[] copy<T>(this IList<T> a) {
        var ret = new T[a.Count];
        for (int i = 0; i < a.Count; i++) ret[i] = a[i];
        return ret;
    }
}

class Scan {
    StreamReader sr;
    public Scan() { sr = new StreamReader(Console.OpenStandardInput()); }
    public Scan(string path) { sr = new StreamReader(path); }
    public int Int => int.Parse(Str);
    public long Long => long.Parse(Str);
    public double Double => double.Parse(Str);
    public string Str => ReadLine.Trim();
    public string ReadLine => sr.ReadLine();
    public pair<T, U> Pair<T, U>() {
        T a; U b;
        Multi(out a, out b);
        return new pair<T, U>(a, b);
    }
    public P P => Pair<int, int>();
    public int[] IntArr => StrArr.Select(int.Parse).ToArray();
    public long[] LongArr => StrArr.Select(long.Parse).ToArray();
    public double[] DoubleArr => StrArr.Select(double.Parse).ToArray();
    public string[] StrArr => Str.Split(new[]{' '}, StringSplitOptions.RemoveEmptyEntries);
    bool eq<T, U>() => typeof(T).Equals(typeof(U));
    T ct<T, U>(U a) => (T)Convert.ChangeType(a, typeof(T));
    T cv<T>(string s) => eq<T, int>()    ? ct<T, int>(int.Parse(s))
                       : eq<T, long>()   ? ct<T, long>(long.Parse(s))
                       : eq<T, double>() ? ct<T, double>(double.Parse(s))
                       : eq<T, char>()   ? ct<T, char>(s[0])
                                         : ct<T, string>(s);
    public void Multi<T>(out T a) => a = cv<T>(Str);
    public void Multi<T, U>(out T a, out U b) {
        var ar = StrArr; a = cv<T>(ar[0]); b = cv<U>(ar[1]);
    }
    public void Multi<T, U, V>(out T a, out U b, out V c) {
        var ar = StrArr; a = cv<T>(ar[0]); b = cv<U>(ar[1]); c = cv<V>(ar[2]);
    }
    public void Multi<T, U, V, W>(out T a, out U b, out V c, out W d) {
        var ar = StrArr; a = cv<T>(ar[0]); b = cv<U>(ar[1]); c = cv<V>(ar[2]); d = cv<W>(ar[3]);
    }
    public void Multi<T, U, V, W, X>(out T a, out U b, out V c, out W d, out X e) {
        var ar = StrArr;
        a = cv<T>(ar[0]); b = cv<U>(ar[1]); c = cv<V>(ar[2]); d = cv<W>(ar[3]); e = cv<X>(ar[4]);
    }
    public void Multi<T, U, V, W, X, Y>(out T a, out U b, out V c, out W d, out X e, out Y f) {
        var ar = StrArr;
        a = cv<T>(ar[0]); b = cv<U>(ar[1]); c = cv<V>(ar[2]);
        d = cv<W>(ar[3]); e = cv<X>(ar[4]); f = cv<Y>(ar[5]);
    }
}