DMOPC '18 Contest 5 P2 - A Photography Problem
View as PDFWhen taking digital photos, it is important to get the proper exposure (brightness). A photo can be represented as a grid of  by 
 pixels, and the pixel in row 
 and column 
 has a brightness 
, which can be any real number from 
 to 
 inclusive. If you average the brightnesses of all the pixels in a typical image, the result is 
. Images whose average is lower than that are underexposed, and those whose average is higher are overexposed.
Most digital cameras have an exposure correction feature. By choosing a correction constant  and multiplying all the pixel brightnesses in an image by 
, a darker or brighter image can be obtained. When applying a correction constant, if any pixel brightnesses become greater than 1, those values are "clipped" and reduced to 1.
Given an image, first determine if it is underexposed, overexposed, or correctly exposed. If the image is not correctly exposed, please find the  that would correct its average brightness to 
. You may consider the image correctly exposed if the required 
 is within 
 of 
.
Constraints
It is guaranteed that no underexposed or overexposed image has a required  within 
 of 
.
Input Specification
The first line will contain two space-separated integers,  and 
.
The next  lines will each contain 
 space-separated real numbers, the pixel brightnesses.
Output Specification
On one line, output the string underexposed, overexposed, or correctly exposed. If the image is not correctly exposed, output an additional line containing one positive real number, the required . Your answer will be considered correct if it has an absolute error of no more than 
.
Sample Input 1
2 3
0.36 0.304 0.12
0.408 0.312 0.96
Sample Output 1
underexposed
1.25
Sample Input 2
2 3
0.48 0.58 0.56
0.38 0.40 0.48
Sample Output 2
correctly exposed
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