public static void main(String[] args)
{
    Scanner in = new Scanner(System.in);
        
    int N = in.nextInt();
    int M = in.nextInt();
        
    int[] arr = new int[N];
        
    int a;
    int b;
    int k;
    while (M-- > 0)
    {
        a = in.nextInt() - 1;
        b = in.nextInt();
        k = in.nextInt();
            
        arr[a] += k;
        if (b < N) arr[b] -= k;
    }
    in.close();
        
    long max = Long.MIN_VALUE;
    long sum = 0;
    for (int value : arr)
    {
        sum += value;
        if (sum > max)
        {
            max = sum;
        }
    }
        
    System.out.println(max);
}