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.*;
import java.math.*;
import java.util.*;
import java.util.concurrent.ArrayBlockingQueue;



public class Main {

    InputReader input;
    PrintWriter output;

    void run(){
        output = new PrintWriter(new OutputStreamWriter(System.out));
        input = new InputReader(System.in);
        solve();
        output.flush();
    }

    public static void main(String[] args){
        new Main().run();
    }
    
    void solve() {
        int n = input.ni();
        int m = input.ni();
        int[] inFlow = new int[n+1];
        int[] outFlow = new int[n+1];
        for(int i = 1; i <= m; i++) {
            int u = input.ni();
            int v = input.ni();
            int c = input.ni();
            inFlow[v] += c;
            outFlow[u] += c;
        }
        int totalDebt = 0;
        for(int i = 1; i <= n; i++) {
            totalDebt += (outFlow[i] - inFlow[i] > 0 ? outFlow[i] - inFlow[i] : 0);
        }
        output.println(totalDebt);
    }

    
    class InputReader {
        private boolean finished = false;
        private InputStream stream;
        private byte[] buf = new byte[1024];
        private int curChar;
        private int numChars;
        private SpaceCharFilter filter;

        public InputReader(InputStream stream) {
                this.stream = stream;
        }

        public int read() {
                if (numChars == -1)
                        throw new InputMismatchException();
                if (curChar >= numChars) {
                        curChar = 0;
                        try {
                                numChars = stream.read(buf);
                        } catch (IOException e) {
                                throw new InputMismatchException();
                        }
                        if (numChars <= 0)
                                return -1;
                }
                return buf[curChar++];
        }

        public int peek() {
                if (numChars == -1)
                        return -1;
                if (curChar >= numChars) {
                        curChar = 0;
                        try {
                                numChars = stream.read(buf);
                        } catch (IOException e) {
                                return -1;
                        }
                        if (numChars <= 0)
                                return -1;
                }
                return buf[curChar];
        }

        public int ni() {
                int c = read();
                while (isSpaceChar(c))
                        c = read();
                int sgn = 1;
                if (c == '-') {
                        sgn = -1;
                        c = read();
                }
                int res = 0;
                do {
                        if (c < '0' || c > '9')
                                throw new InputMismatchException();
                        res *= 10;
                        res += c - '0';
                        c = read();
                } while (!isSpaceChar(c));
                return res * sgn;
        }

        public long nl() {
                int c = read();
                while (isSpaceChar(c))
                        c = read();
                int sgn = 1;
                if (c == '-') {
                        sgn = -1;
                        c = read();
                }
                long res = 0;
                do {
                        if (c < '0' || c > '9')
                                throw new InputMismatchException();
                        res *= 10;
                        res += c - '0';
                        c = read();
                } while (!isSpaceChar(c));
                return res * sgn;
        }

        public String ns() {
                int c = read();
                while (isSpaceChar(c))
                        c = read();
                StringBuilder res = new StringBuilder();
                do {
                        res.appendCodePoint(c);
                        c = read();
                } while (!isSpaceChar(c));
                return res.toString();
        }

        public boolean isSpaceChar(int c) {
                if (filter != null)
                        return filter.isSpaceChar(c);
                return isWhitespace(c);
        }

        public boolean isWhitespace(int c) {
                return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
        }

        private String readLine0() {
                StringBuilder buf = new StringBuilder();
                int c = read();
                while (c != '\n' && c != -1) {
                        if (c != '\r')
                                buf.appendCodePoint(c);
                        c = read();
                }
                return buf.toString();
        }

        public String readLine() {
                String s = readLine0();
                while (s.trim().length() == 0)
                        s = readLine0();
                return s;
        }

        public String readLine(boolean ignoreEmptyLines) {
                if (ignoreEmptyLines)
                        return readLine();
                else
                        return readLine0();
        }

        public BigInteger readBigInteger() {
                try {
                        return new BigInteger(ns());
                } catch (NumberFormatException e) {
                        throw new InputMismatchException();
                }
        }

        public char readCharacter() {
                int c = read();
                while (isSpaceChar(c))
                        c = read();
                return (char) c;
        }

        public double readDouble() {
                int c = read();
                while (isSpaceChar(c))
                        c = read();
                int sgn = 1;
                if (c == '-') {
                        sgn = -1;
                        c = read();
                }
                double res = 0;
                while (!isSpaceChar(c) && c != '.') {
                        if (c == 'e' || c == 'E')
                                return res * Math.pow(10, ni());
                        if (c < '0' || c > '9')
                                throw new InputMismatchException();
                        res *= 10;
                        res += c - '0';
                        c = read();
                }
                if (c == '.') {
                        c = read();
                        double m = 1;
                        while (!isSpaceChar(c)) {
                                if (c == 'e' || c == 'E')
                                        return res * Math.pow(10, ni());
                                if (c < '0' || c > '9')
                                        throw new InputMismatchException();
                                m /= 10;
                                res += (c - '0') * m;
                                c = read();
                        }
                }
                return res * sgn;
        }

        public boolean eof() {
                int value;
                while (isSpaceChar(value = peek()) && value != -1)
                        read();
                return value == -1;
        }

        public String next() {
                return ns();
        }

        public SpaceCharFilter getFilter() {
                return filter;
        }

        public void setFilter(SpaceCharFilter filter) {
                this.filter = filter;
        }
       
    }
     public interface SpaceCharFilter {
         public boolean isSpaceChar(int ch);
     }

}