403. Scientific Problem
Time limit per test: 0.25 second(s)Memory limit: 65536 kilobytes
input: standardoutput: standard
Once upon a time Professor Idioticideasinventor was travelling by train. Watching cheerless landscape outside the window, he decided to invent the theme of his new scientific work. All of a sudden a brilliant idea struck him: to develop an effective algorithm finding an integer number, which isxtimes less than the sum of all its integer positive predecessors, where numberxis given. As far as he has no computer in the train, you have to solve this difficult problem.
Input
The first line of the input file contains an integer numberx(1 ≤x≤ 109).
Output
Output an integer number— the answer to the problem.
Example(s)
sample inputsample output
13
sample inputsample output
25
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思路：先给出一个数x，求出数n，使得n是n之前所有数(包括n)的总和的1/x
由求和公式n*(n+1)/2/x = n 可得 n=2*x+1
AC代码：
#include <cstdio>#include <cstring>#include <algorithm>using namespace std;int main() {int x;while(scanf("%d", &x) != EOF) {printf("%d\n", 2*x+1);}return 0;}
，以后我会去到很多很繁华或苍凉，
