Nội dung Bài tập
Mã:
POSTERIZE
Tên:
Posterize (World Final 2017_F)
Dạng thi:
acm
Thang điểm:
1 điểm
Giới hạn thời gian:
2 giây
Giới hạn bộ nhớ:
256 MB
Được tạo bởi:
pvtran1995
Pixels in a digital picture can be represented with three integers in the range 0 to 255 that indicate the
intensity of the red, green, and blue colors. To compress an image or to create an artistic effect, many
photo-editing tools include a “posterize” operation which works as follows. Each color channel is examined separately; this problem focuses only on the red channel. Rather than allow all integers from
0 to 255 for the red channel, a posterized image allows at most k integers from this range. Each pixel’s original red intensity is replaced with the nearest of the allowed integers. The photo-editing tool selects a set of k integers that minimizes the sum of the squared errors introduced across all pixels in the original image. If there are pixels that have original red values r1,.....,rn, and k allowed integers v1,.....,vk, the sum of squared errors is defined as  
Your task is to compute the minimum achievable sum of squared errors, given parameter k and a description of the red intensities of an image’s pixels.

Input
The first line of the input contains two integers d (1 d 256), the number of distinct red values that occur in the original image, and k (1 k d), the number of distinct red values allowed in the posterized image. The remaining d lines indicate the number of pixels of the image having various red values. Each such line contains two integers r (0 r 255) and p (1 p 226), where r is a red intensity value and p is the number of pixels having red intensity r. Those d lines are given in increasing order of red value.

Output
Display the sum of the squared errors for an optimally chosen set of k allowed integer values.
  
Sample1

InputOutput
2 1
50 20000
150 10000
66670000


Sample2

InputOutput
2 2
50 20000
150 10000
0


Sample3

InputOutput
4 2
0 30000
25 30000
50 30000
255 30000
37500000



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