public class ArrayManipulation {
    // https://www.hackerrank.com/challenges/crush/problem

    public ArrayManipulation() {
        Scanner scanner = new Scanner(System.in);
        int n = scanner.nextInt();
        int m = scanner.nextInt();
        int[] array = new int[n];

        for (int i = 0 ; i < m; i++) {
            int a = scanner.nextInt() - 1;
            int b = scanner.nextInt() - 1;
            int k = scanner.nextInt();

            for (int j = a; j <= b; j++) {
                array[j] += k;
            }
        }

        scanner.close();

        // Find max value of array
        int maxValue = array[0];
        for(int i = 1; i < array.length; i++){
            if(array[i] > maxValue){
                maxValue = array[i];
            }
        }

        System.out.println(maxValue);
    }
}