# 月度存档: 1月 2011

## SGU 114 解题报告

http://acm.sgu.ru/problem.php?contest=0&problem=114

## 114. Telecasting station

time limit per test: 0.50 sec.
memory limit per test: 4096 KB

Every city in Berland is situated on Ox axis. The government of the country decided to build new telecasting station. After many experiments Berland scientists came to a conclusion that in any city citizens displeasure is equal to product of citizens amount in it by distance between city and TV-station. Find such point on Ox axis for station so that sum of displeasures of all cities is minimal.

### Input

Input begins from line with integer positive number N (0<N<15000) – amount of cities in Berland. Following N pairs (X, P) describes cities (0<X, P<50000), where X is a coordinate of city and P is an amount of citizens. All numbers separated by whitespace(s).

### Output

Write the best position for TV-station with accuracy 10-5.

### Sample Input

4
1 3
2 1
5 2
6 2


### Sample Output

3.00000


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## SGU 144 解题报告

http://acm.sgu.ru/problem.php?contest=0&problem=144

## 144. Meeting

time limit per test: 0.50 sec.
memory limit per test: 4096 KB

Two of the three members of the winning team of one of the ACM regional contests are going to meet in order to train for the upcoming World Finals. They decided that they will meet sometime between X o’clock and Y o’clock. Because they never get anywhere on time (they were late even on the day of the regional contest), they did not set an exact time when they will meet. However, they decided that the one who gets first at the meeting point will not wait more than Z minutes for the other one (they calculated that, if the other one will not come within Z minutes from the arrival of the first of them, then it is very probable that he will not show up at all).
Knowing that, in the end, both of them will show up at some time between X o’clock and Y o’clock (not necessarily after an integer number of minutes), compute which is the probability that they will actually meet.

### Input

The input will contain 2 integer numbers X and Y (0<=X<Y<=24) and one real number Z ( 0 < Z <= 60*(Y-X) ).

### Output

You should output the required probability with 7 decimal digits (rounded according to the 8th decimal digit).

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## .Net程序员:最简单方式掌握Linux本质(转载)

“If you can’t explain it simply, you don’t understand it well enough” Albert Einstein

Linux的配置文件就相当于注册表的键,或者说Linux采用是的分布式的注册表.

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