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.lang.*;
import java.io.*;  
public class Main 
{
/*
    HashMap<> map=new HashMap<>();
    TreeMap<> map=new TreeMap<>();
    map.put(p,map.getOrDefault(p,0)+1);
    for(Map.Entry<> mx:map.entrySet()){
          int v=mx.getValue(),k=mx.getKey();
    }for (int i = 1; i <= 1000; i++)
    fac[i] = fac[i - 1] * i % mod;
    ArrayList<Pair<Character,Integer>> l=new ArrayList<>();
    ArrayList<> l=new ArrayList<>();
    HashSet<> has=new HashSet<>();*/ 
    PrintWriter out;
    FastReader sc;
    long mod=(long)(1e9+7);
    int maxint= Integer.MAX_VALUE;
    int minint= Integer.MIN_VALUE;
    long maxlong=Long.MAX_VALUE;
    long minlong=Long.MIN_VALUE;  
    int find(long[][] ar,long a,int m){
          int l=0,r=m-1;
          while(l<r){
                int mid=l+(r-l)/2;
                if(ar[mid][0]>=a){
                      r=mid;
                }else{
                      l=mid+1;
                }
          }if(ar[l][0]<a)return -1;
          return l;
    }
    public void sol(){
          int testCase=ni();  
          while(testCase-->0){
                int n=ni(),m=ni();
                long[][] ar=new long[m][2];
                for(int i=0;i<m;i++){
                      ar[i][0]=nl();
                      ar[i][1]=nl();
                }
                Arrays.sort(ar,new Comparator<long[]>(){
                       public int compare(long[] a,long[] b){
                             if(a[0]==b[0]){
                                   return Long.compare(a[1],b[1]);
                             }else return Long.compare(a[0],b[0]);
                       }   
                });long[] sum=new long[m];
                sum[0]=ar[0][0];
                long ans=0;
                if(n<=m){
                      for(int i=m-1;i>=(m-n);i--){
                            ans+=ar[i][0];
                      }
                }
                for(int i=1;i<m;i++){
                      sum[i]=sum[i-1]+ar[i][0];
                }for(int i=0;i<m;i++){
                      int p=find(ar,ar[i][1],m);
                      if(p==-1){
                            ans=max(ans,ar[i][0]+(n-1)*ar[i][1]);
                      }else if(p>i&&(n-(m-p)-1)>=0){
                            ans=max(ans,sum[m-1]-sum[p-1]+ar[i][0]+(n-(m-p)-1)*ar[i][1]);
                      }else if(p==i&&(n-(m-p))>=0){
                            if(i!=0){
                            ans=max(ans,sum[m-1]-sum[p-1]+(n-(m-p))*ar[i][1]);
                            }
                            else{
                              ans=max(ans,sum[m-1]+(n-(m-p))*ar[i][1]);
                            }
                      }else if((n-(m-p))>=0){
                            if(p>=1)
                            ans=max(ans,sum[m-1]-sum[p-1]+(n-(m-p))*ar[i][1]);
                            else{
                                  ans=max(ans,sum[m-1]+(n-(m))*ar[i][1]);
                            }
                      }
                }pl(ans);
                rl1();
          }
    }
    public static void main(String[] args) 
	{ 
	      Main g=new Main();
		g.out=new PrintWriter(System.out);
		g.sc=new FastReader();
		g.sol();
		g.out.flush();
	}
	static class FastReader 
	{ 
		BufferedReader br; 
		StringTokenizer st; 
 
		public FastReader() 
		{ 
			br = new BufferedReader(new
					InputStreamReader(System.in)); 
		} 
 
		String next() 
		{ 
			while (st == null || !st.hasMoreElements()) 
			{ 
				try
				{ 
					st = new StringTokenizer(br.readLine()); 
				} 
				catch (IOException e) 
				{ 
					e.printStackTrace(); 
				} 
			} 
			return st.nextToken(); 
		} 
 
		int nextInt() 
		{ 
			return Integer.parseInt(next()); 
		} 
 
		long nextLong() 
		{ 
			return Long.parseLong(next()); 
		} 
 
		double nextDouble() 
		{ 
			return Double.parseDouble(next()); 
		} 
 
		String nextLine() 
		{ 
			String str = ""; 
			try
			{ 
				str = br.readLine(); 
			} 
			catch (IOException e) 
			{ 
				e.printStackTrace(); 
			} 
			return str; 
		} 
	} public int ni(){
	      return sc.nextInt();
	}public long nl(){
	      return sc.nextLong();
	}public double nd(){
	      return sc.nextDouble();
	}public char[] rl(){
	      return sc.nextLine().toCharArray();
	}public String rl1(){
	      return sc.nextLine();
	}
	public void pl(Object s){
	      out.println(s);
	}public void ex(){
	      out.println();
	}
	public void pr(Object s){
	      out.print(s);
	}public String next(){
	      return sc.next();
	}public long abs(long x){
	      return Math.abs(x);
	}
	public int abs(int x){
	      return Math.abs(x);
	}
	public double abs(double x){
	      return Math.abs(x);
	}
      public long pow(long x,long y){
            return (long)Math.pow(x,y);
      }
      public int pow(int x,int y){
            return (int)Math.pow(x,y);
      }
      public double pow(double x,double y){
            return Math.pow(x,y);
      }public long min(long x,long y){
            return (long)Math.min(x,y);
      }
      public int min(int x,int y){
            return (int)Math.min(x,y);
      }
      public double min(double x,double y){
            return Math.min(x,y);
      }public static int gcd(int a, int b) {
		if (a == 0)
			return b;
		return gcd(b % a, a);
	}static void sort(int[] a) {
		ArrayList<Integer> l = new ArrayList<>();
		for (int i : a) {
			l.add(i);
		}
		Collections.sort(l);
		for (int i = 0; i < a.length; i++) {
			a[i] = l.get(i);
		}
	}void sort(long[] a) {
		ArrayList<Long> l = new ArrayList<>();
		for (long i : a) {
			l.add(i);
		}
		Collections.sort(l);
		for (int i = 0; i < a.length; i++) {
			a[i] = l.get(i);
		}
	}void sort(double[] a) {
		ArrayList<Double> l = new ArrayList<>();
		for (double i : a) {
			l.add(i);
		}
		Collections.sort(l);
		for (int i = 0; i < a.length; i++) {
			a[i] = l.get(i);
		}
	}int  swap(int a,int b){
	      return a;
	}long  swap(long a,long b){
	      return a;
	}double  swap(double a,double b){
	      return a;
	}
	boolean isPowerOfTwo (int x) 
      { 
            return x!=0 && ((x&(x-1)) == 0);     
      }boolean isPowerOfTwo (long x) 
      { 
            return x!=0 && ((x&(x-1)) == 0);     
      }public long max(long x,long y){
            return (long)Math.max(x,y);
      }
      public int max(int x,int y){
            return (int)Math.max(x,y);
      }
      public double max(double x,double y){
            return Math.max(x,y);
      }long sqrt(long x){
            return (long)Math.sqrt(x);
      }int sqrt(int x){
            return (int)Math.sqrt(x);
      }void input(int[] ar,int n){
            for(int i=0;i<n;i++)ar[i]=ni();
      }void input(long[] ar,int n){
            for(int i=0;i<n;i++)ar[i]=nl();
      }void fill(int[] ar,int k){
            Arrays.fill(ar,k);
      }void yes(){
            pl("YES");
      }void no(){
            pl("NO");
      }
    int[] sieve(int n) 
    { 
        boolean prime[] = new boolean[n+1]; 
        int[] k=new int[n+1];
        for(int i=0;i<=n;i++) {
            prime[i] = true; 
            k[i]=i;
        }
          
        for(int p = 2; p <=n; p++) 
        { 
            if(prime[p] == true) 
            { 
               // sieve[p]=p;
                for(int i = p*2; i <= n; i += p) {
                    prime[i] = false; 
                  //  sieve[i]=p;
                    while(k[i]%(p*p)==0){
                          k[i]/=(p*p);
                    }
                }
            } 
        }return k;
    }int strSmall(int[] arr, int target)  
    {  
        int start = 0, end = arr.length-1;  
        int ans = -1;  
        while (start <= end) {  
            int mid = (start + end) / 2;   
            if (arr[mid] >= target) {  
                end = mid - 1;  
            }   
            else {  
                ans = mid;  
                start = mid + 1;  
            }  
        }  
        return ans;  
    } int strSmall(ArrayList<Integer> arr, int target)  
    {  
        int start = 0, end = arr.size()-1;  
        int ans = -1;  
        while (start <= end) {  
            int mid = (start + end) / 2;   
            if (arr.get(mid) > target) {  
                start = mid + 1; 
                ans=start;
            }   
            else {
                end = mid - 1;  
            }  
        }  
        return ans;  
    }long mMultiplication(long a,long b) 
    { 
        long res = 0;    
        a %= mod; 
  
        while (b > 0)  
        {  
            if ((b & 1) > 0)  
            { 
                res = (res + a) % mod; 
            }  
            a = (2 * a) % mod; 
  
            b >>= 1;  
        } 
        return res; 
    }long nCr(int n, int r,
                             long p)
    {
 
          if (n<r) 
              return 0;
        if (r == 0)
            return 1;
            long[] fac = new long[n + 1];
        fac[0] = 1;
 
        for (int i = 1; i <= n; i++)
            fac[i] = fac[i - 1] * i % p;
        return (fac[n] * modInverse(fac[r], p)
                % p * modInverse(fac[n - r], p)
                % p)
            % p;
    }long power(long x, long y, long p)
    {
        long res = 1;
        x = x % p;
 
        while (y > 0) {
            if (y % 2 == 1)
                res = (res * x) % p;
            y = y >> 1; 
            x = (x * x) % p;
        }
 
        return res;
    }long modInverse(long n, long p)
    {
        return power(n, p - 2, p);
    }
      public static class Pair implements Comparable<Pair> {
		int x;
		int y;
 
		public Pair(int x, int y) {
			this.x = x;
			this.y = y;
		}
 
		public String toString() {
			return x + "," + y;
		}
 
		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 Double(x).hashCode() * 31 + new Double(y).hashCode();
		}
 
		public int compareTo(Pair other) {
			if (this.x == other.x) {
				return Long.compare(this.y, other.y);
			}
			return Long.compare(this.x, other.x);
		}
      }
	 
} 