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:
import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.util.StringTokenizer;

public class Main {
	
	public static boolean debug = false;
	public static Reader in = new Reader();
	public static Writer out = new Writer();
	
	public static void main(String[] args) {
		int n = in.nextInt();
		int m = in.nextInt();
		
		int[] debts = new int[n];
		
		while(m-->0) {
			int x = in.nextInt()-1;
			int y = in.nextInt()-1;
			int c = in.nextInt();
			debts[x] += c;
			debts[y] -= c;
			//out.println(Arrays.toString(debts));
		}
		
		int total = 0;
		
		for(int i=0; i<n; i++) {
			if(debts[i] < 0) {
				total -= debts[i];
			}
		}
		
		out.println(total);
		out.close();
	}
}

class Writer {
	
	private BufferedWriter output;
	
	public Writer() {
		output = new BufferedWriter(new OutputStreamWriter(System.out));
	}
	
	public Writer(String s) {
		try {
			output = new BufferedWriter(new FileWriter(s));
		} catch(Exception ex) { ex.printStackTrace(); System.exit(0);}
	}
	
	public void println() {
		try {
			output.append("\n");
		} catch(IOException io) { io.printStackTrace(); System.exit(0);}
	}

	public void print(Object o) {
		try {
			output.append(o.toString());
		} catch(IOException io) { io.printStackTrace(); System.exit(0);}
	}
	
	public void println(Object o) {
		try {
			output.append(o.toString()+"\n");
		} catch(IOException io) { io.printStackTrace(); System.exit(0);}
	}

	public void printf(String format, Object... args) {
		try {
			output.append(String.format(format, args));
		} catch(IOException io) { io.printStackTrace(); System.exit(0);}
	}
	
	public void printfln(String format, Object... args) {
		try {
			output.append(String.format(format, args)+"\n");
		} catch(IOException io) { io.printStackTrace(); System.exit(0);}
	}
	
	public void flush() {
		try {
			output.flush();
		} catch(IOException io) { io.printStackTrace(); System.exit(0);}
	}
	
	public void close() {
		try {
			output.close();
		} catch(IOException io) { io.printStackTrace(); System.exit(0);}
	}
}

class Reader {
	private BufferedReader input;
	private StringTokenizer line = new StringTokenizer("");
	
	public Reader() {
		input = new BufferedReader(new InputStreamReader(System.in));
	}

	public Reader(String s) {
		try {
			input = new BufferedReader(new FileReader(s));
		} catch(IOException io) { io.printStackTrace(); System.exit(0);}
	}
	
	public void fill() {
		try {
			if(!line.hasMoreTokens()) line = new StringTokenizer(input.readLine());
		} catch(IOException io) { io.printStackTrace(); System.exit(0);}
	}
	
	public double nextDouble() {
		fill();
		return Double.parseDouble(line.nextToken());
	}
	
	public String nextWord() {
		fill();
		return line.nextToken();
	}
	
	public int nextInt() {
		fill();
		return Integer.parseInt(line.nextToken());
	}

	public long nextLong() {
		fill();
		return Long.parseLong(line.nextToken());
	}
	
	public double readDouble() {
		double d = 0;
		try {
			d = Double.parseDouble(input.readLine());
		} catch(IOException io) {io.printStackTrace(); System.exit(0);}
		return d;
	}
	
	public int readInt() {
		int i = 0;
		try {
			i = Integer.parseInt(input.readLine());
		} catch(IOException io) {io.printStackTrace(); System.exit(0);}
		return i;
	}
	
	public int[] readInts(int n) {
		int[] a = new int[n];
		for(int i=0; i<n; i++)
			a[i] = nextInt();
		return a;
	}
	
	public void fillInts(int[] a) {
		for(int i=0; i<a.length; i++)
			a[i] = nextInt();
	}
	
	public long readLong() {
		long l = 0;
		try {
			l = Long.parseLong(input.readLine());
		} catch(IOException io) {io.printStackTrace(); System.exit(0);}
		return l;
	}
	
	public String readLine() {
		String s = "";
		try {
			s = input.readLine();
		} catch(IOException io) {io.printStackTrace(); System.exit(0);}
		return s;
	}
}