Vladimir would like to prepare a present for his wife: they have an anniversary! He decided to buy her exactly n flowers.

Vladimir went to a flower shop, and he was amazed to see that there are m types of flowers being sold there, and there is unlimited supply of flowers of each type. Vladimir wants to choose flowers to maximize the happiness of his wife. He knows that after receiving the first flower of the i-th type happiness of his wife increases by a_i and after receiving each consecutive flower of this type her happiness increases by b_i. That is, if among the chosen flowers there are x_i > 0 flowers of type i, his wife gets a_i + (x_i - 1) ⋅ b_i additional happiness (and if there are no flowers of type i, she gets nothing for this particular type).

Please help Vladimir to choose exactly n flowers to maximize the total happiness of his wife.

Input

The first line contains the only integer t (1 ≤ t ≤ 10 000), the number of test cases. It is followed by t descriptions of the test cases.

Each test case description starts with two integers n and m (1 ≤ n ≤ 10^9, 1 ≤ m ≤ 100 000), the number of flowers Vladimir needs to choose and the number of types of available flowers.

The following m lines describe the types of flowers: each line contains integers a_i and b_i (0 ≤ a_i, b_i ≤ 10^9) for i-th available type of flowers.

The test cases are separated by a blank line. It is guaranteed that the sum of values m among all test cases does not exceed 100 000.

Output

For each test case output a single integer: the maximum total happiness of Vladimir's wife after choosing exactly n flowers optimally.

Example

Input


2
4 3
5 0
1 4
2 2

5 3
5 2
4 2
3 1


Output


14
16

Note

In the first example case Vladimir can pick 1 flower of the first type and 3 flowers of the second type, in this case the total happiness equals 5 + (1 + 2 ⋅ 4) = 14.

In the second example Vladimir can pick 2 flowers of the first type, 2 flowers of the second type, and 1 flower of the third type, in this case the total happiness equals (5 + 1 ⋅ 2) + (4 + 1 ⋅ 2) + 3 = 16.
import javax.security.auth.login.CredentialNotFoundException;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Comparator;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.StringTokenizer;
import java.util.TreeMap;

public class Main implements Runnable {
    int n, m, k;
    static boolean use_n_tests = true;
    int[][][] dp;
    int mod = 1000_000_007;

    void solve(FastScanner in, PrintWriter out, int testNumber) {
        int n = in.nextInt();
        m = in.nextInt();
        Ab[] ab = new Ab[m];
        for (int i = 0; i < m; i++) {
            int a = in.nextInt();
            int b = in.nextInt();
            ab[i] = new Ab(a, b, i);
        }
        Arrays.sort(ab, Comparator.comparing(Ab::getA));
        for (int i = 0; i < m; i++) {
            ab[i].sum = ab[i].a;
            if (i > 0) {
                ab[i].sum += ab[i - 1].sum;
            }
        }
        long result = 0;
        for (int i = 0; i < m; i++) {
            long curB = ab[i].b;
            int l = 0;
            int r = m - 1;
            int ans = -1;
            while (l <= r) {
                int mid = (l + r) / 2;
                if (ab[mid].a >= curB) {
                    ans = mid;
                    l = mid + 1;
                } else {
                    r = mid - 1;
                }
            }
            int take = ans + 1;
            int add = 0;
            if (i > ans) {
                add = ab[i].a;
                take++;
            }
            long sum = 0;
            if (ans != -1) {
                sum = ab[ans].sum;
            }
            if (n <= take) {
                result = Math.max(result, ab[n - 1].sum);
            } else {
                result = Math.max(result, sum + add + curB * (n - take));
            }
        }
        out.println(result);
    }

    class Ab {
        public Ab(int a, int b, int id) {
            this.a = a;
            this.b = b;
            this.id = id;
        }

        int id;

        public int getA() {
            return -a;
        }

        int a, b;

        long sum;

        public int getB() {
            return b;
        }
    }

    // ****************************** template code ***********
    List<Integer> getGidits(long n) {
        List<Integer> res = new ArrayList<>();
        while (n != 0) {
            res.add((int) (n % 10L));
            n /= 10;
        }
        return res;
    }

    List<Integer> generatePrimes(int n) {
        List<Integer> res = new ArrayList<>();
        boolean[] sieve = new boolean[n + 1];
        for (int i = 2; i <= n; i++) {
            if (!sieve[i]) {
                res.add(i);
            }
            if ((long) i * i <= n) {
                for (int j = i * i; j <= n; j += i) {
                    sieve[j] = true;
                }
            }
        }
        return res;
    }

    int ask(int l, int r) {
        if (l >= r) {
            return -1;
        }
        System.out.printf("? %d %d\n", l + 1, r + 1);
        System.out.flush();
        return in.nextInt() - 1;
    }

    static int stack_size = 1 << 27;

    class Mod {
        long mod;

        Mod(long mod) {
            this.mod = mod;
        }

        long add(long a, long b) {
            a = mod(a);
            b = mod(b);
            return (a + b) % mod;
        }

        long sub(long a, long b) {
            a = mod(a);
            b = mod(b);
            return (a - b + mod) % mod;
        }

        long mul(long a, long b) {
            a = mod(a);
            b = mod(b);
            return a * b % mod;
        }

        long div(long a, long b) {
            a = mod(a);
            b = mod(b);
            return (a * inv(b)) % mod;
        }

        public long inv(long r) {
            if (r == 1)
                return 1;
            return ((mod - mod / r) * inv(mod % r)) % mod;
        }

        private long mod(long a) {
            return a % mod;
        }
    }

    static class Coeff {
        long mod;
        long[][] C;
        long[] fact;
        boolean cycleWay = false;

        Coeff(int n, long mod) {
            this.mod = mod;
            fact = new long[n + 1];
            fact[0] = 1;
            for (int i = 1; i <= n; i++) {
                fact[i] = i;
                fact[i] %= mod;
                fact[i] *= fact[i - 1];
                fact[i] %= mod;
            }
        }

        Coeff(int n, int m, long mod) {
            // n > m
            cycleWay = true;
            this.mod = mod;
            C = new long[n + 1][m + 1];
            for (int i = 0; i <= n; i++) {
                for (int j = 0; j <= Math.min(i, m); j++) {
                    if (j == 0 || j == i) {
                        C[i][j] = 1;
                    } else {
                        C[i][j] = C[i - 1][j - 1] + C[i - 1][j];
                        C[i][j] %= mod;
                    }
                }
            }
        }

        public long C(int n, int m) {
            if (cycleWay) {
                return C[n][m];
            }
            return fC(n, m);
        }

        private long fC(int n, int m) {
            return (fact[n] * inv(fact[n - m] * fact[m] % mod)) % mod;
        }

        private long inv(long r) {
            if (r == 1)
                return 1;
            return ((mod - mod / r) * inv(mod % r)) % mod;
        }
    }

    class Pair {
        int first;
        long second;

        Pair(int f, long s) {
            first = f;
            second = s;
        }

        public int getFirst() {
            return first;
        }

        public long getSecond() {
            return second;
        }
    }

    class MultisetTree<T> {
        int size = 0;

        TreeMap<T, Integer> mp = new TreeMap<>();

        void add(T x) {
            mp.merge(x, 1, Integer::sum);
            size++;
        }

        void remove(T x) {
            if (mp.containsKey(x)) {
                mp.merge(x, -1, Integer::sum);
                if (mp.get(x) == 0) {
                    mp.remove(x);
                }
                size--;
            }
        }

        boolean contains(T x) {
            return mp.containsKey(x);
        }

        T greatest() {
            return mp.lastKey();
        }

        T smallest() {
            return mp.firstKey();
        }

        int size() {
            return size;
        }

        int diffSize() {
            return mp.size();
        }
    }

    class Multiset<T> {
        int size = 0;

        Map<T, Integer> mp = new HashMap<>();

        void add(T x) {
            mp.merge(x, 1, Integer::sum);
            size++;
        }

        boolean contains(T x) {
            return mp.containsKey(x);
        }

        void remove(T x) {
            if (mp.containsKey(x)) {
                mp.merge(x, -1, Integer::sum);
                if (mp.get(x) == 0) {
                    mp.remove(x);
                }
                size--;
            }
        }

        int size() {
            return size;
        }

        int diffSize() {
            return mp.size();
        }
    }

    static class Range {
        int l, r;
        int id;

        public int getL() {
            return l;
        }

        public int getR() {
            return r;
        }

        public Range(int l, int r, int id) {
            this.l = l;
            this.r = r;
            this.id = id;
        }
    }

    static class Array {
        static Range[] readRanges(int n, FastScanner in) {
            Range[] result = new Range[n];
            for (int i = 0; i < n; i++) {
                result[i] = new Range(in.nextInt(), in.nextInt(), i);
            }
            return result;
        }

        static List<List<Integer>> intInit2D(int n) {
            List<List<Integer>> res = new ArrayList<>();
            for (int i = 0; i < n; i++) {
                res.add(new ArrayList<>());
            }
            return res;
        }

        static boolean isSorted(Integer[] a) {
            for (int i = 0; i < a.length - 1; i++) {
                if (a[i] > a[i + 1]) {
                    return false;
                }
            }
            return true;
        }

        static public long sum(int[] a) {
            long sum = 0;
            for (int x : a) {
                sum += x;
            }
            return sum;
        }

        static public long sum(long[] a) {
            long sum = 0;
            for (long x : a) {
                sum += x;
            }
            return sum;
        }

        static public long sum(Integer[] a) {
            long sum = 0;
            for (int x : a) {
                sum += x;
            }
            return sum;
        }

        static public int min(Integer[] a) {
            int mn = Integer.MAX_VALUE;
            for (int x : a) {
                mn = Math.min(mn, x);
            }
            return mn;
        }

        static public int min(int[] a) {
            int mn = Integer.MAX_VALUE;
            for (int x : a) {
                mn = Math.min(mn, x);
            }
            return mn;
        }

        static public int max(Integer[] a) {
            int mx = Integer.MIN_VALUE;
            for (int x : a) {
                mx = Math.max(mx, x);
            }
            return mx;
        }

        static public int max(int[] a) {
            int mx = Integer.MIN_VALUE;
            for (int x : a) {
                mx = Math.max(mx, x);
            }
            return mx;
        }

        static public int[] readint(int n, FastScanner in) {
            int[] out = new int[n];
            for (int i = 0; i < out.length; i++) {
                out[i] = in.nextInt();
            }
            return out;
        }
    }

    class Graph {
        List<List<Integer>> graph;

        Graph(int n) {
            create(n);
        }

        private void create(int n) {
            List<List<Integer>> graph = new ArrayList<>();
            for (int i = 0; i < n; i++) {
                graph.add(new ArrayList<>());
            }
            this.graph = graph;
        }

        void readBi(int m, FastScanner in) {
            for (int i = 0; i < m; i++) {
                int v = in.nextInt() - 1;
                int u = in.nextInt() - 1;
                graph.get(v).add(u);
                graph.get(u).add(v);
            }
        }
    }

    class FastScanner {
        BufferedReader br;
        StringTokenizer st;

        public FastScanner(InputStream io) {
            br = new BufferedReader(new InputStreamReader(io));
        }

        public String line() {
            String result = "";
            try {
                result = br.readLine();
            } catch (IOException e) {
                e.printStackTrace();
            }
            return result;
        }

        public String next() {
            while (st == null || !st.hasMoreElements()) {
                try {
                    st = new StringTokenizer(br.readLine());
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            return st.nextToken();
        }

        public char[] nextc() {
            return next().toCharArray();
        }

        public int nextInt() {
            return Integer.parseInt(next());
        }

        public int[] nextArray(int n) {
            int[] res = new int[n];
            for (int i = 0; i < n; i++) {
                res[i] = in.nextInt();
            }
            return res;
        }

        public long[] nextArrayL(int n) {
            long[] res = new long[n];
            for (int i = 0; i < n; i++) {
                res[i] = in.nextLong();
            }
            return res;
        }

        public Long[] nextArrayL2(int n) {
            Long[] res = new Long[n];
            for (int i = 0; i < n; i++) {
                res[i] = in.nextLong();
            }
            return res;
        }


        public Integer[] nextArray2(int n) {
            Integer[] res = new Integer[n];
            for (int i = 0; i < n; i++) {
                res[i] = in.nextInt();
            }
            return res;
        }

        public long nextLong() {
            return Long.parseLong(next());
        }

    }

    void run_t_tests() {
        int t = in.nextInt();
        int i = 0;
        while (t-- > 0) {
            solve(in, out, i++);
        }
    }

    void run_one() {
        solve(in, out, -1);
    }

    @Override
    public void run() {
        in = new FastScanner(System.in);
        out = new PrintWriter(System.out);
        if (use_n_tests) {
            run_t_tests();
        } else {
            run_one();
        }
        out.close();
    }

    static FastScanner in;
    static PrintWriter out;

    public static void main(String[] args) throws InterruptedException {
        Thread thread = new Thread(null, new Main(), "", stack_size);
        thread.start();
        thread.join();
    }
}