G. Calculating Max Grade
time limit per test
1 second
memory limit per test
256 megabytes
input
standard input
output
standard output

John is pursuing a degree in environmental science. This semester, he has taken $$$N$$$ courses. In course $$$i$$$, John received a score of $$$v_i$$$ and earned $$$u_i$$$ units. John chooses $$$K$$$ of his $$$N$$$ courses, and his final grade is calculated as the sum of the scores in his chosen courses divided by the sum of the units earned in his chosen courses: $$$\frac{\sum_{i=1}^N v_i}{\sum_{i=1}^N u_i}$$$. Find the maximum final grade John can obtain in this manner.

Input

Line $$$1$$$: Two space separated positive integers, $$$N$$$ and $$$K$$$ ($$$1 \le K \le N \le 10^5$$$), where $$$N$$$ is the number of courses John took and $$$K$$$ is the number of courses he must choose in calculating his grade.

Lines $$$2…N+1$$$: Two space separated positive integers, $$$u_i$$$ and $$$v_i$$$ ($$$1 \le u_i, v_i \le 10^6$$$), where $$$u_i$$$ is the number of units he earned and $$$v_i$$$ is the score John received in course $$$i$$$.

Output

Line $$$1$$$: The maximum grade John can obtain using the described grading system, rounded to six decimal places.

Example
Input
3 2
2 2
5 3
2 1
Output
0.750000