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 $a_2+a_3+a_4+a_5+a_7=10+(-8)+5+9+(-6)=10$.