Consider a string of length ~N~ consisting of 0 and 1. The score for the string is calculated as follows:

• For each ~i~ ~(1 \le i \le M)~, ~a_i~ is added to the score if the string contains 1 at least once between the ~l_i~-th and ~r_i~-th characters (inclusive).

Find the maximum possible score of a string.

Constraints

• All values in input are integers.
• ~1 \le N \le 2 \times 10^5~
• ~1 \le M \le 2 \times 10^5~
• ~1 \le l_i \le r_i \le N~
• ~|a_i| \le 10^9~

Input Specification

The first line will contain two integers ~N~ and ~M~.

The next ~M~ lines will each contain three integers, ~l_i, r_i, a_i~.

Output Specification

Print the maximum possible score of a string.

Sample Input 1

5 3
1 3 10
2 4 -10
3 5 10

Sample Output 1

20

Explanation For Sample 1

The score for 10001 is ~a_1 + a_3 = 10 + 10 = 20~.

Sample Input 2

3 4
1 3 100
1 1 -10
2 2 -20
3 3 -30

Sample Output 2

90

Explanation For Sample 2

The score for 100 is ~a_1 + a_2 = 100 + (-10) = 90~.

Sample Input 3

1 1
1 1 -10

Sample Output 3

0

Explanation For Sample 3

The score for 0 is ~0~.

Sample Input 4

1 5
1 1 1000000000
1 1 1000000000
1 1 1000000000
1 1 1000000000
1 1 1000000000

Sample Output 4

5000000000

Explanation For Sample 4

The answer may not fit into a 32-bit integer type.

Sample Input 5

6 8
5 5 3
1 1 10
1 6 -8
3 6 5
3 4 9
5 5 -2
1 3 -6
4 6 -7

Sample Output 5

10

Explanation For Sample 5

For example, the score for 101000 is ~a_2 + a_3 + a_4 + a_5 + a_7 = 10 + (-8) + 5 + 9 + (-6) = 10~.