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.Closeable;
import java.io.Flushable;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.util.StringTokenizer;

public class Main {
	static Reader in = new Reader(System.in);
	static Writer out = new Writer(System.out);

	/*
	5 3
	1 2 10 -> 1: -10, 2: +10
	2 3 4 -> 2: +6, 3: +4
	2 4 1 -> 2: +5, 4: +1
	4 1 3 -> 4: -2, 1: -7
	 */

	public static void main(String[] args) throws IOException {

		// read input
		int n = in.nextInt();
		int m = in.nextInt();

		int[] balance = new int[n];
		for (int i = 0; i < m; i++) {
			int[] pay = in.nextIntArray(3);
			balance[pay[0]-1] -= pay[2];
			balance[pay[1]-1] += pay[2];

//			System.out.println(Arrays.toString(balance));
		}

		int res = 0;
		for (int i = 0; i < n; i++) {
			if (balance[i] < 0) {
				res += balance[i];
			}
		}

		// print output
		out.print(-res);

		// close stuff
		in.close();
		out.flush();
		out.close();
	}

	private static boolean isOddNumberOfToggles(int n) {
		int res = 1; // last walk always toggle
		for (int i = 1; i < Math.sqrt(n) +1; i++) {
			if (n%i == 0) res++;
		}
		return res % 2 != 0;
	}

	static class Reader implements Closeable {

		private final BufferedReader reader;
		private StringTokenizer tokenizer;

		public Reader(InputStream input) {
			reader = new BufferedReader(
					new InputStreamReader(input));
			tokenizer = new StringTokenizer("");
		}

		private StringTokenizer getTokenizer() throws IOException {
			if (tokenizer == null || !tokenizer.hasMoreTokens()) {
				String line = nextLine();
				if (line == null) {
					return null;
				}
				tokenizer = new StringTokenizer(line);
			}
			return tokenizer;
		}

		public boolean hasNext() throws IOException {
			return getTokenizer() != null;
		}

		public String next() throws IOException {
			return hasNext() ? tokenizer.nextToken() : null;
		}

		public String nextLine() throws IOException {
			tokenizer = null;
			return reader.readLine();
		}

		public int nextInt() throws IOException {
			return Integer.parseInt(next());
		}

		public long nextLong() throws IOException {
			return Long.parseLong(next());
		}

		public float nextFloat() throws IOException {
			return Float.parseFloat(next());
		}

		public double nextDouble() throws IOException {
			return Double.parseDouble(next());
		}

		public String[] nextStringArray(int size) throws IOException {
			String[] array = new String[size];
			for (int i = 0; i < size; i++) {
				array[i] = next();
			}
			return array;
		}

		public int[] nextIntArray(int size) throws IOException {
			int[] array = new int[size];
			for (int i = 0; i < size; i++) {
				array[i] = nextInt();
			}
			return array;
		}

		public long[] nextLongArray(int size) throws IOException {
			long[] array = new long[size];
			for (int i = 0; i < size; i++) {
				array[i] = nextLong();
			}
			return array;
		}

		public double[] nextDoubleArray(int size) throws IOException {
			double[] array = new double[size];
			for (int i = 0; i < size; i++) {
				array[i] = nextDouble();
			}
			return array;
		}

		@Override
		public void close() throws IOException {
			tokenizer = null;
			reader.close();
		}
	}

	static class Writer implements Closeable, Flushable {

		private final PrintWriter writer;

		public Writer(OutputStream outputStream) {
			writer = new PrintWriter(new BufferedWriter(new OutputStreamWriter(outputStream)));
		}

		public void print(Object... objects) {
			for (int i = 0; i < objects.length; i++) {
				if (i != 0) {
					writer.print(' ');
				}
				writer.print(objects[i]);
			}
		}

		public void println(Object... objects) {
			print(objects);
			writer.println();
		}

		@Override
		public void close() {
			writer.close();
		}

		@Override
		public void flush() {
			writer.flush();
		}
	}


}