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 java.util.*;


import java.io.*;


public class C {
    
    static int mod = (int) (1e9+7);
    static InputReader in;
    static PrintWriter out;
    static Pair[] list;
    static long[] sum;
    static int n;
    static int m;
    
    static long getValue(int i, int j) {
    	int k = n - j;
    	long x = sum[k];
    	if(i <= k) {
    		x -= list[i - 1].x;
			x += list[k].x;
    	}
    	long y = list[i - 1].x + list[i - 1].y * 1l* (j - 1);
    	return x + y;
    }
    
    static long getPeak(int i, int l, int r) {
    	long max = 0;
    	while(r - l >= 0) {
    		int mid1 = l + (r - l) / 3;
    		int mid2 = r - (r - l) / 3;
    		long val1 = getValue(i, mid1);
    		long val2 = getValue(i, mid2);
    		max = max(val1, val2);
    		if(val1 > val2) {
    			r = mid2 - 1;
    		}
    		else l = mid1 + 1;
    	}
    	return max;
    }

    
    static void solve()
    {
 
        in = new InputReader(System.in);
        out = new PrintWriter(System.out); 
        
        int t = in.nextInt();
        
        while(t-- > 0) {
        	n = in.nextInt();
        	m = in.nextInt();
        	
        	list = new Pair[m];
        	sum = new long[m + 1];
        	
        	for(int i = 0; i < m; i++) {
        		list[i] = new Pair(in.nextInt(), in.nextInt());
        	}
        	Arrays.sort(list);
        	for(int i = 0; i < m; i++) {
        		sum[i + 1] = sum[i] + list[i].x;        		
        	}
//        	long[][] dp = new long[m + 1][n + 1];
        	long ans = 0;
        	for(int i = 1; i <= m; i++) {
        		long pos = getValue(i, n);
        		long neg = getValue(i, max(n - m + 1, 1));
        		long peak = getPeak(i, max(n - m + 1, 1), n);
        		ans = max(ans, max(max(pos, neg), peak));
//        		debug(pos, neg, max);
//        		for(int j = n - m + 1; j <= n; j++) {
//        			dp[i][j] = getValue(i, j);
//        		}
//        		debug(dp[i]);
        	}
        	out.println(ans);
        }
        
        
        out.close();
        
    }
    
    public static void main(String[] args) {
        new Thread(null ,new Runnable(){
            public void run()
            {
                try{
                    solve();
                } catch(Exception e){
                    e.printStackTrace();
                }
            }
        },"1",1<<26).start();
    }
    
    static int[][] graph(int from[], int to[], int n)
    {
        int g[][] = new int[n][];
        int cnt[] = new int[n];
        for (int i = 0; i < from.length; i++) {
            cnt[from[i]]++;
            cnt[to[i]]++;
        }
        for (int i = 0; i < n; i++) {
            g[i] = new int[cnt[i]];
        }
        Arrays.fill(cnt, 0);
        for (int i = 0; i < from.length; i++) {
            g[from[i]][cnt[from[i]]++] = to[i];
            g[to[i]][cnt[to[i]]++] = from[i];
        }
        return g;
    }
    
    static class Pair implements Comparable<Pair>{

        int x,y;
        

		Pair (int x,int y){
			this.x=x;
			this.y=y;
		}
	        
		public int compareTo(Pair o) {
			return -Integer.compare(this.x,o.x);
			//return 0;
		}

        public boolean equals(Object o) {
            if (o instanceof Pair) {
                Pair p = (Pair)o;
                return p.x == x && p.y == y;
            }
            return false;
        }
        public int hashCode() {
            return new Integer(x).hashCode() * 31 + new Integer(y).hashCode();
        }
        @Override
        public String toString() {
        	return x + " " + y;
        }
    } 
    
    static String rev(String s) {
        StringBuilder sb = new StringBuilder(s);
        sb.reverse();
        return sb.toString();
    }

    static long gcd(long x, long y) {
        if (y == 0) {
            return x;
        } else {
            return gcd(y, x % y);
        }
    }

    static int gcd(int x, int y) {
        if (y == 0) {
            return x;
        } else {
            return gcd(y, x % y);
        }
    }
    
    static int abs(int a, int b) {
        return (int) Math.abs(a - b);
    }

    static long abs(long a, long b) {
        return (long) Math.abs(a - b);
    }

    static int max(int a, int b) {
        if (a > b) {
            return a;
        } else {
            return b;
        }
    }

    static int min(int a, int b) {
        if (a > b) {
            return b;
        } else {
            return a;
        }
    }

    static long max(long a, long b) {
        if (a > b) {
            return a;
        } else {
            return b;
        }
    }

    static long min(long a, long b) {
        if (a > b) {
            return b;
        } else {
            return a;
        }
    }

    static long pow(long n, long p, long m) {
        long result = 1;
        if (p == 0) {
            return 1;
        }
        while (p != 0) {
            if (p % 2 == 1) {
                result *= n;
            }
            if (result >= m) {
                result %= m;
            }
            p >>= 1;
            n *= n;
            if (n >= m) {
                n %= m;
            }
        }
        return result;
    }

    static long pow(long n, long p) {
        long result = 1;
        if (p == 0) {
            return 1;
        }
        if (p == 1) {
            return n;
        }
        while (p != 0) {
            if (p % 2 == 1) {
                result *= n;
            }
            p >>= 1;
            n *= n;
        }
        return result;
    }
   
    static void debug(Object... o) {
            System.out.println(Arrays.deepToString(o));
    }

    static class InputReader
    {

        private final InputStream stream;
        private final byte[] buf = new byte[8192];
        private int curChar, snumChars;
        private SpaceCharFilter filter;

        public InputReader(InputStream stream)
        {
                this.stream = stream;
        }

        public int snext()
        {
                if (snumChars == -1)
                        throw new InputMismatchException();
                if (curChar >= snumChars)
                {
                        curChar = 0;
                        try
                        {
                                snumChars = stream.read(buf);
                        } catch (IOException e)
                        {
                                throw new InputMismatchException();
                        }
                        if (snumChars <= 0)
                                return -1;
                }
                return buf[curChar++];
        }

        public int nextInt()
        {
                int c = snext();
                while (isSpaceChar(c))
                {
                        c = snext();
                }
                int sgn = 1;
                if (c == '-')
                {
                        sgn = -1;
                        c = snext();
                }
                int res = 0;
                do
                {
                        if (c < '0' || c > '9')
                                throw new InputMismatchException();
                        res *= 10;
                        res += c - '0';
                        c = snext();
                } while (!isSpaceChar(c));
                return res * sgn;
        }

        public long nextLong()
        {
                int c = snext();
                while (isSpaceChar(c))
                {
                        c = snext();
                }
                int sgn = 1;
                if (c == '-')
                {
                        sgn = -1;
                        c = snext();
                }
                long res = 0;
                do
                {
                        if (c < '0' || c > '9')
                                throw new InputMismatchException();
                        res *= 10;
                        res += c - '0';
                        c = snext();
                } while (!isSpaceChar(c));
                return res * sgn;
        }

        public int[] nextIntArray(int n)
        {
                int a[] = new int[n];
                for (int i = 0; i < n; i++)
                {
                        a[i] = nextInt();
                }
                return a;
        }

        public long[] nextLongArray(int n)
        {
                long a[] = new long[n];
                for (int i = 0; i < n; i++)
                {
                        a[i] = nextLong();
                }
                return a;
        }

        public String readString()
        {
                int c = snext();
                while (isSpaceChar(c))
                {
                        c = snext();
                }
                StringBuilder res = new StringBuilder();
                do
                {
                        res.appendCodePoint(c);
                        c = snext();
                } while (!isSpaceChar(c));
                return res.toString();
        }

        public String nextLine()
        {
                int c = snext();
                while (isSpaceChar(c))
                        c = snext();
                StringBuilder res = new StringBuilder();
                do
                {
                        res.appendCodePoint(c);
                        c = snext();
                } while (!isEndOfLine(c));
                return res.toString();
        }

        public boolean isSpaceChar(int c)
        {
                if (filter != null)
                        return filter.isSpaceChar(c);
                return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
        }

        private boolean isEndOfLine(int c)
        {
                return c == '\n' || c == '\r' || c == -1;
        }

        public interface SpaceCharFilter
        {
                public boolean isSpaceChar(int ch);
        }

    }
}    

