The 15th UESTC Programming Contest Preliminary D - Destr0y City cdoj1558

地址：http://acm.uestc.edu.cn/#/problem/show/1558

题目：

D - Destr0y City

Time Limit: 3000/1000MS (Java/Others)     Memory Limit: 65535/65535KB (Java/Others)

Alice want to build nn cities on a plane. A city can be regarded as a point. In order to keep communication between cities, the distance between each pair of cities must NOT greater than DD.

Bob has a weapon which can destroy all the cities in a circle with radius RR. After Alice building all the cities, Bob will select a city as the center and use his weapon once, and he will choose a way such that can destroy as many cities as possible.

To prevent the cities from being destroyed, Alice want choose a way to build her cities such that the number of cities will be destroyed by Bob can be as little as possible, can you tell her how to build these cities?

In order to make the problem easier, you can assume that D=2√RD=2R is always established, so the specific values of DD and RR will not affect the answer.

Input

Only one line contains an integer nn.

1≤n≤10181≤n≤1018.

Output

The number of cities will be destroyed by Bob if Alice choose the optimal scheme to build her cities.

Sample input and output

Sample Input	Sample Output
3	1

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思路：找规律，猜结论

#include<iostream>
using namespace std;
long long n;
int main()
{
   cin>>n;
   cout<<n/3+!(!(n%3));
}