## 2spooky4me

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Points: 7
Time limit: 1.0s
Memory limit: 16M

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Problem type
##### PEG Test - Halloween 2014

Kenny wants to go trick-or-treating too! But the street has many spooky decorations put up on it. Kenny doesn't like to be scared, so he avoids spooky areas.

There are houses arranged in a line on the street, numbered from 1 to . Each house will give exactly 1 unit of candy to Kenny. There are spooky decorations on this street. The -th decoration covers the street from house number to , inclusive, raising the spookiness of those houses by spookiness units.

Kenny will be too scared to knock on any doors if the spookiness of a house is greater than or equal to . The spookiness of a house is the sum of the spookinesses of all the decorations passing through it.

Determine the amount of candy Kenny can receive from all the houses on the street.

#### Input Specification

The first line of input will contain the integers: , , .
The next lines of input will contain values , and for each house. .

#### Output Specification

Output a single integer, the amount of candy that Kenny can get.

#### Sample Input 1

3 100 10
20 59 4
30 69 4
40 79 4

#### Sample Output 1

80

#### Explanation 1

Houses between number 40 and 59 inclusive have a spookiness of 12, which is 2spooky for Kenny. He can still get candy from houses 1 to 39, and 60 to 100.

#### Sample Input 2

2 10 4
3 5 2
5 7 2

#### Sample Output 2

9

#### Explanation 2

Only house 5 is 2spooky for Kenny.