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 templates;

import java.io.*;
import java.util.Scanner;
import java.util.StringTokenizer;

import static java.lang.System.in;

public class Olimpiad {

    public static void main(String[] args) throws IOException {
        Solve solve = new Solve(new ConsoleIOFast());
        solve.getSolve();
    }
}

interface TypeIO {

    void solve() throws IOException;
}

class FileIO implements TypeIO {

    @Override
    public void solve() throws IOException {
        Scanner sc = new Scanner(new File("input.txt"));
        PrintWriter pw = new PrintWriter(new File("output.txt"));
        /*
            todo write code
         */
        sc.close();
        pw.close();
    }
}

class ConsoleIOFast implements TypeIO {

    BufferedReader in;
    StringTokenizer tok;
    PrintWriter out;

    String readToken() throws IOException {
        while (tok == null || !tok.hasMoreTokens()) {
            tok = new StringTokenizer(in.readLine());
        }
        return tok.nextToken();
    }

    int readInt() throws IOException {
        return Integer.parseInt(readToken());
    }

    String readString() throws IOException {
        return readToken();
    }

    @Override
    public void solve() throws IOException {
        in = new BufferedReader(new InputStreamReader(System.in));
        out = new PrintWriter(System.out);
        /*
            todo write code
         */
        int n = readInt();
        int m = readInt();
        long answer = 0;
        int ans[] = new int[n + 1];
        for(int i = 0; i < m; i++){
            int a = readInt();
            int b = readInt();
            int c = readInt();
            ans[a] += c;
            ans[b] -= c;
        }
        for(int value : ans){
            if(value > 0){
                answer += value;
            }
        }
        System.out.println(answer);
        out.close();
        in.close();
    }
}

class ConsoleIO implements TypeIO {

    @Override
    public void solve() throws IOException {
        Scanner sc = new Scanner(in);
        /*
            todo write code
         */
        sc.close();
    }
}

class Solve {

    private TypeIO typeIO;

    public Solve(TypeIO typeIO) {
        this.typeIO = typeIO;
    }

    void getSolve() throws IOException {
        typeIO.solve();
    }
}

class Folder implements Comparable<Folder>{
    public int id;
    public int l;
    public int r;

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

    @Override
    public int compareTo(Folder o) {
        return this.id - o.id;
    }
}