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 Main {
    static class Scan {
        private byte[] buf=new byte[1024];
        private int index;
        private InputStream in;
        private int total;
        public Scan()
        {
            in=System.in;
        }
        public int scan()throws IOException
        {
            if(total<0)
            throw new InputMismatchException();
            if(index>=total)
            {
                index=0;
                total=in.read(buf);
                if(total<=0)
                return -1;
            }
            return buf[index++];
        }
        public int scanInt()throws IOException
        {
            int integer=0;
            int n=scan();
            while(isWhiteSpace(n))
            n=scan();
            int neg=1;
            if(n=='-')
            {
                neg=-1;
                n=scan();
            }
            while(!isWhiteSpace(n))
            {
                if(n>='0'&&n<='9')
                {
                    integer*=10;
                    integer+=n-'0';
                    n=scan();
                }
                else throw new InputMismatchException();
            }
            return neg*integer;
        }
        public double scanDouble()throws IOException
        {
            double doub=0;
            int n=scan();
            while(isWhiteSpace(n))
            n=scan();
            int neg=1;
            if(n=='-')
            {
                neg=-1;
                n=scan();
            }
            while(!isWhiteSpace(n)&&n!='.')
            {
                if(n>='0'&&n<='9')
                {
                    doub*=10;
                    doub+=n-'0';
                    n=scan();
                }
                else throw new InputMismatchException();
            }
            if(n=='.')
            {
                n=scan();
                double temp=1;
                while(!isWhiteSpace(n))
                {
                    if(n>='0'&&n<='9')
                    {
                        temp/=10;
                        doub+=(n-'0')*temp;
                        n=scan();
                    }
                    else throw new InputMismatchException();
                }
            }
            return doub*neg;
        }
        public String scanString()throws IOException
        {
            StringBuilder sb=new StringBuilder();
            int n=scan();
            while(isWhiteSpace(n))
            n=scan();
            while(!isWhiteSpace(n))
            {
                sb.append((char)n);
                n=scan();
            }
            return sb.toString();
        }
        private boolean isWhiteSpace(int n)
        {
            if(n==' '||n=='\n'||n=='\r'||n=='\t'||n==-1)
            return true;
            return false;
        }
    }
    public static void main(String args[]) throws IOException {
        Scan input=new Scan();
        int test=input.scanInt();
        StringBuilder ans=new StringBuilder("");
        for(int t=1;t<=test;t++) {
            int n=input.scanInt();
            int m=input.scanInt();
            long arr[]=new long[m];
            long brr[]=new long[m];
            for(int i=0;i<m;i++) {
                arr[i]=input.scanInt();
                brr[i]=input.scanInt();
            }
            ans.append(solve(arr,brr,n,m)+"\n");
        }
        System.out.println(ans);
    }
    public static long solve(long arr[],long brr[],long n,int m) {
        sort(arr,brr,m);
        long ans=0;
        long prefix[]=new long[m];
        prefix[0]=arr[0];
        for(int i=1;i<m;i++) {
            prefix[i]=prefix[i-1]+arr[i];
        }
        for(int i=0;i<m;i++) {
            int indx=next(arr,brr[i]);
            if(indx==-1) {
                ans=Math.max(ans,arr[i]+(n-1)*brr[i]);
                continue;
            }
            int ele=m-indx;
            if(ele>n) {
                continue;
            }
            if(ele==n) {
                ans=Math.max(ans, sum(prefix,indx,m-1));
            }
            else {
                if(arr[i]>=brr[i]) {
                    ans=Math.max(ans, sum(prefix,indx,m-1)+(n-ele)*brr[i]);
                }
                else {
                    ans=Math.max(ans, sum(prefix,indx,m-1)+arr[i]+(n-ele-1)*brr[i]);
                }
            }
        }
        for(int i=m-1;i>=0;i--) {
            int ele=m-i;
            if(ele==n) {
                ans=Math.max(ans,sum(prefix,i,m-1));
            }
        }
        return ans;
    }
    public static long sum(long prefix[],int l,int r) {
        return prefix[r]-(l==0?0:prefix[l-1]);
    }
    static int next(long[] arr, long target)  
    {  
        int start = 0, end = arr.length - 1;  
    
        int ans = -1;  
        while (start <= end) {  
            int mid = (start + end) / 2;  
    
            // Move to right side if target is  
            // greater.  
            if (arr[mid] < target) {  
                start = mid + 1;  
            }  
    
            // Move left side.  
            else {  
                ans = mid;  
                end = mid - 1;  
            }  
        }  
        return ans;  
    }  
    
    
    static void buildMaxHeap(long arr[],long brr[], int n) 
  { 
    for (int i = 1; i < n; i++) 
    { 
      // if child is bigger than parent 
      if (arr[i] > arr[(i - 1) / 2]) 
      { 
        int j = i; 
  
        // swap child and parent until 
        // parent is smaller 
        while (arr[j] > arr[(j - 1) / 2]) 
        { 
          swap(arr, j, (j - 1) / 2); 
          swap(brr, j, (j - 1) / 2); 
          j = (j - 1) / 2; 
        } 
      } 
    } 
  } 
  
  static void sort(long arr[],long brr[], int n) 
  { 
    buildMaxHeap(arr,brr, n); 
  
    for (int i = n - 1; i > 0; i--) 
    { 
      // swap value of first indexed 
      // with last indexed 
      swap(arr, 0, i); 
      swap(brr, 0, i); 
  
      // maintaining heap property 
      // after each swapping 
      int j = 0, index; 
  
      do
      { 
        index = (2 * j + 1); 
  
        // if left child is smaller than 
        // right child point index variable 
        // to right child 
        if (index < (i - 1) && arr[index] < arr[index + 1]) 
          index++; 
  
        // if parent is smaller than child 
        // then swapping parent with child 
        // having higher value 
        if (index < i && arr[j] < arr[index]) {
          swap(arr, j, index); 
          swap(brr, j, index);
        }
  
        j = index; 
  
      } while (index < i); 
    } 
  } 
  
  public static void swap(long[] a, int i, int j) { 
    long temp = a[i]; 
    a[i]=a[j]; 
    a[j] = temp; 
  } 
}
