Problem: Imagine that there is a group of three friends: A, B and С. A owes B 20 rubles and B owes C 20 rubles. The total sum of the debts is 40 rubles. You can see that the debts are not organized in a very optimal manner. Let's rearrange them like that: assume that A owes C 20 rubles and B doesn't owe anything to anybody. The debts still mean the same but the total sum of the debts now equals 20 rubles.

This task is a generalisation of a described example. Imagine that your group of friends has n people and you know the debts between the people. Optimize the given debts without changing their meaning. In other words, finally for each friend the difference between the total money he should give and the total money he should take must be the same. Print the minimum sum of all debts in the optimal rearrangement of the debts. See the notes to the test samples to better understand the problem.

Input

The first line contains two integers n and m (1 ≤ n ≤ 100; 0 ≤ m ≤ 104). The next m lines contain the debts. The i-th line contains three integers ai, bi, ci (1 ≤ ai, bi ≤ n; ai ≠ bi; 1 ≤ ci ≤ 100), which mean that person ai owes person bi ci rubles.

Assume that the people are numbered by integers from 1 to n.

It is guaranteed that the same pair of people occurs at most once in the input. The input doesn't simultaneously contain pair of people (x, y) and pair of people (y, x).

Output

Print a single integer — the minimum sum of debts in the optimal rearrangement.

Examples

Input

5 3
1 2 10
2 3 1
2 4 1


Output

10


Input

3 0


Output

0


Input

4 3
1 2 1
2 3 1
3 1 1


Output

0

Note

In the first sample, you can assume that person number 1 owes 8 rubles to person number 2, 1 ruble to person number 3 and 1 ruble to person number 4. He doesn't owe anybody else anything. In the end, the total debt equals 10.

In the second sample, there are no debts.

In the third sample, you can annul all the debts.

Solution (in JAVA):

Solution:
//package credit;

import java.io.*;
import java.util.*;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.Scanner;
import java.util.StringTokenizer;
public class sas {
    static boolean v[];
    static int ans[];
    int size[];
    static int count=0;
    static int dsu=0;
    static int c=0;
    int min=Integer.MAX_VALUE;
    int max1=Integer.MIN_VALUE;
    int max=Integer.MIN_VALUE;
    boolean aBoolean=true;
    PrintWriter printWriter = new PrintWriter(System.out);
        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;
            }
        }
        int parent[];
        int rank[];
        public static void main(String[] args) throws IOException {
            sas g = new sas();
            g.go();
        }
        public void go() throws IOException {
            FastReader scanner=new FastReader();
//            Scanner scanner=new Scanner(System.in);
            int t =1;
            long c1=0;
            for (int i = 0; i < t; i++) {
                int n=scanner.nextInt();
                int m=scanner.nextInt();
                int arr[]=new int[n+1];
                long sum=0;
                for (int j = 0; j < m; j++) {
                    int a=scanner.nextInt();
                    int b=scanner.nextInt();
                    int c=scanner.nextInt();
                    arr[a]+=(-c);
                    arr[b]+=(c);
                }
                for (int j = 0; j < n+1; j++) {
                    if(arr[j]>0)
                    sum+=arr[j];
                }
                printWriter.println(sum);
            }
            printWriter.flush();
        }
        public void parent(int n){
            for (int i = 0; i < n; i++) {
                parent[i]=i;
                rank[i]=1;
                size[i]=1;
            }
        }
        public void union(int i,int j){
            int root1=find(i);
            int root2=find(j);
//            if(root1 != root2) {
//                parent[root2] = root1;
////                sz[a] += sz[b];
//            }
            if(root1==root2){
                return;
            }
            if(rank[root1]>rank[root2]){
                parent[root2]=root1;
                size[root1]+=size[root2];
            }
            else if(rank[root1]<rank[root2]){
                parent[root1]=root2;
                size[root2]+=size[root1];
            }
            else{
                parent[root2]=root1;
                rank[root1]+=1;
                size[root1]+=size[root2];
            }
        }
        public int find(int p){
           if(parent[p]!=p){
               parent[p]=find(parent[p]);
           }
           return parent[p];
//            if(parent[p]==-1){
//                return -1;
//            }
//            else if(parent[p]==p){
//                return p;
//            }
//            else {
//                parent[p]=find(parent[p]);
//                return parent[p];
//            }
        }
        public double dist(int x1,int y1,int x2,int y2){
            double e=(x2-x1)*(x2-x1)+(y2-y1)*(y2-y1);
            double e1=Math.sqrt(e);
            return e1;
        }
        public void make(int p){
            parent[p]=p;
            rank[p]=1;
        }
        Random rand = new Random();
        public void sort(long[] a, int n) {
                for (int i = 0; i < n; i++) {
                   int j = rand.nextInt(i + 1);
                   long tmp = a[i];
                   a[i] = a[j];
                   a[j] = tmp;
                }
                Arrays.sort(a, 0, n);
        }
        public long gcd(long a,long b){
               if(b==0){
                  return a;
               }
               return gcd(b,a%b);
        }
        private void dfs2(ArrayList<Integer>[]arrayList,int j,int count){
            ans[j]=count;
            for(int i:arrayList[j]){
                if(ans[i]==-1){
                    dfs2(arrayList,i,count);
                }
            }
        }
        private void dfs(ArrayList<Integer>[] arrayList, int j) {
            v[j]=true;
            count++;
            for(int i:arrayList[j]){
                if(v[i]==false) {
                    dfs(arrayList, i);
                }
            }
        }
        public double fact(double h){
            double sum=1;
            while(h>=1){
                sum=sum*h;
                h--;
            }
            return sum;
        }
        public long primef(double r){
            long c=0;
            while(r%2==0){
                c++;
                r=r/2;
            }
            for (int i = 3; i <=Math.sqrt(r) ;i+=2) {
                while(r%i==0){
                    c++;
                    r=r/3;
                }
            }
            if(r>2){
                c++;
            }
            return c;
        }
}

class Pair{
    double x;
    double y;
    public Pair(double x,double y){
        this.x=x;
        this.y=y;
    }
}
class Sorting implements Comparator<Pair> {
    public int compare(Pair p1,Pair p2){
        if(p1.y==p2.y){
            return Double.compare(p1.x,p2.x);
        }
        else {
            return -1*Double.compare(p1.y, p2.y);
        }
    }

}