Nội dung Bài tập
Mã:
SCENERY
Tên:
Scenery (World Final 2017_H)
Dạng thi:
acm
Thang điểm:
1 điểm
Giới hạn thời gian:
6 giây
Giới hạn bộ nhớ:
256 MB
Được tạo bởi:
pvtran1995
You have decided to spend a day of your trip to Rapid City taking photographs of the South Dakota Badlands, which are renowned for their spectacular and unusual land formations. You are an amateur photographer, yet very particular about lighting conditions.

After some careful research, you have located a beautiful location in the Badlands, surrounded by picturesque landscapes. You have determined a variety of features that you wish to photograph from this location. For each feature you have identified the earliest and latest time of day at which the position of the sun is ideal. However, it will take quite a bit of time to take each photograph, given the need to reposition the tripod and camera and your general perfectionism. So you are wondering if it will be possible to successfully take photographs of all these features in one day.  

Input
The first line of the input contains two integers n (1 n 104) and t (1 t 105), where n is the number
of desired photographs and t is the time you spend to take each photograph. Following that are additional lines, each describing the available time period for one of the photographs. Each such line contains two nonnegative integers a and b, where a is the earliest time that you may begin working on that photograph, and b is the time by which the photograph must be completed, with a + t b 109.

Output
Display yes if it is possible to take all n photographs, and no otherwise  

Sample1

InputOutput
2 10
0 15
5 20
yes


Sample2

InputOutput
2 10
1 15
0 20
no


Sample3

InputOutput
2 10
5 30
10 20
yes


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