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:
// Working program with FastReader 
import java.io.*;
import java.util.*;
public class ll
{ 
    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; 
        } 
    } 

    static final int MAXN = 100001;
    // stores smallest prime factor for every number
    static int spf[] = new int[MAXN];
    // Calculating SPF (Smallest Prime Factor) for every
    // number till MAXN.
    // Time Complexity : O(nloglogn)
    static void sieve()
    {
        spf[1] = 1;
        for (int i=2; i<MAXN; i++)

        // marking smallest prime factor for every
        // number to be itself.
            spf[i] = i;

        // separately marking spf for every even
        // number as 2
        for (int i=4; i<MAXN; i+=2)
            spf[i] = 2;

        for (int i=3; i*i<MAXN; i++)
        {
            // checking if i is prime
            if (spf[i] == i)
            {
                // marking SPF for all numbers divisible by i
                for (int j=i*i; j<MAXN; j+=i)

                // marking spf[j] if it is not
                // previously marked
                    if (spf[j]==j)
                        spf[j] = i;
            }
        }
    }
    // A O(log n) function returning primefactorization
    // by dividing by smallest prime factor at every step
    static int getFactorization(int x)
    {
        int c=0;
        while (x != 1)
        {
            c++;
            x = x / spf[x];
        }
        return c;
    }

    /*
    static int LowerBound(int a[], int x) { // x is the target value or key
    int l=-1,r=a.length;
    while(l+1<r) {
    int m=(l+r)>>>1;
    if(a[m]>=x) r=m;
    else l=m;
    }
    return r;
    }

    static int UpperBound(int a[], int x) {// x is the key or target value
    int l=-1,r=a.length;
    while(l+1<r) {
    int m=(l+r)>>>1;
    if(a[m]<=x) l=m;
    else r=m;
    }
    return l+1;
    }
     */
    static int gcd(int a, int b)
    {
        if (a == 0)
            return b; 
        return gcd(b % a, a); 
    }

    // method to return LCM of two numbers
    static int lcm(int a, int b)
    {
        return (a / gcd(a, b)) * b;
    }

    public static int[] swap(int a[], int left, int right)
    {
        int temp = a[left];
        a[left] = a[right];
        a[right] = temp;
        return a;
    }

    public static int[] reverse(int a[], int left, int right)
    {
        // Reverse the sub-array
        while (left < right) {
            int temp = a[left];
            a[left++] = a[right];
            a[right--] = temp;
        }
        return a;
    }

    public static int[] findNextPermutation(int a[])
    {
        int last = a.length - 2;

        // find the longest non-increasing suffix
        // and find the pivot
        while (last >= 0) {
            if (a[last] < a[last + 1]) {
                break;
            }
            last--;
        }

        // If there is no increasing pair
        // there is no higher order permutation
        if (last < 0)
            return a;

        int nextGreater = a.length - 1;

        // Find the rightmost successor to the pivot
        for (int i = a.length - 1; i > last; i--) {
            if (a[i] > a[last]) {
                nextGreater = i;
                break;
            }
        }

        // Swap the successor and the pivot
        a = swap(a, nextGreater, last);

        // Reverse the suffix
        a = reverse(a, last + 1, a.length - 1);

        // Return true as the next_permutation is done
        return a;
    }

    static void sort(int[] a) {
        ArrayList<Integer> l = new ArrayList<>();
        for (int i : a)
            l.add(i);
        Collections.sort(l);
        for (int i = 0; i < a.length; i++)
            a[i] = l.get(i);
    }

    static double pow(double p,double tt)
    {
        double ii,q,r;
        q=1;
        r=p;
        while(tt>1)
        {
            for(ii=1;2*ii<=tt;ii*=2)
                p*=p;
            tt-=ii;
            q*=p;
            p=r;
        }
        if(tt==1)
            q*=r;
        return q;
    }

    static long pow(long p,long tt,long mod)
    {
        long ii,q,r;
        q=1l;
        r=p;
        while(tt>1)
        {
            for(ii=1l;2*ii<=tt;ii*=2l)
                p=((p%mod)*(p%mod))%mod;
            tt-=ii;
            q=((q%mod)*(p%mod))%mod;
            p=r;
        }
        if(tt==1)
            q=((q%mod)*(r%mod))%mod;
        return q;
    }

    static int factorial(int n)
    {
        return (n == 1 || n == 0) ? 1 : n * factorial(n - 1);
    }

    public static long primeFactors(long n)
    {
        long c=0l;
        long max=0l;
        long z=0l;
        //ArrayList <Integer> ll=new ArrayList<>();
        // Print the number of 2s that divide n
        while (n%2==0)
        {
            c++;
            n /= 2l;
            //ll.add(2);
        }
        if(c>max)
        {
            max=c;
            z=2;
        }
        // n must be odd at this point.  So we can
        // skip one element (Note i = i +2)
        for (int i = 3; i <= Math.sqrt(n); i+= 2)
        {
            // While i divides n, print i and divide n
            c=0;
            while (n%i == 0)
            {
                c++;
                n /= i;
                //ll.add(i);
            }
            if(c>max)
            {
                max=c;
                z=i;
            }
        }
        c=0;
        // This condition is to handle the case whien
        // n is a prime number greater than 2
        if (n > 2)
        {
            c++;
            //ll.add((int)n);
        }
        if(c>max)
        {
            max=c;
            z=n;
        }
        return z;
    }
    static void PrimeList(){
        int i,j;
        int sieve[]=new int[100001];
        for(i=2;i*i<=100000;i++)
        {
            if(sieve[i]==0)
            {
                for(j=i*i;j<=100000;j+=i)
                    sieve[j]=1;
            }
        }
        ArrayList<Integer> primes=new ArrayList<>();
        for(i=2;i<=100000;i++)
        {
            if(sieve[i]==0)
                primes.add(i);
        }
    }

    static int comp(int a[],int b[],int n)
    {
        int z=0;
        for(int i=0;i<n;i++)
        {
            if(a[i]!=b[i])
            {
                z=1;
                break;
            }
        }
        if(z==0)
            return 1;
        else
            return 0;
    }

    public static void main(String[] args) 
    {
        //try
        //{
        FastReader d=new FastReader();
        PrintWriter pr = new PrintWriter(new BufferedWriter(new OutputStreamWriter(System.out)));
        int t,i,j,k,l,r,n;
        int mod = (int) 1e9 + 7;

        int Inf=Integer.MAX_VALUE;
        int negInf=Integer.MIN_VALUE;
        //t=d.nextInt();
        t=1;
        //String s;
        //char ch1,ch2,ch3,ch4;
        long ans,c,z;
        
        while(t-->0)
        {
            z=c=0l;
            ans=0l;
            n=d.nextInt();
            int m=d.nextInt();
            int a[]=new int[m];
            int b[]=new int[m];
            int co[]=new int[m];
            for(i=0;i<m;i++)
            {
                a[i]=d.nextInt();
                b[i]=d.nextInt();
                co[i]=d.nextInt();
            }
            int x[]=new int[n+1];
            for(i=0;i<m;i++)
            {
                x[a[i]]+=co[i];
                x[b[i]]-=co[i];
            }
            for(i=0;i<=n;i++)
            {
                if(x[i]>0)
                ans+=x[i];
            }
            System.out.println(ans);
            //dont need extra d.nextLine()
        }
        /*
        }catch(Exception e)  {
        System.out.println(0);
        }*/
        pr.flush();
    }
}