Codeforces Round #569 (Div. 2) A. Alex and a Rhombus

Codeforces Round #569 (Div. 2)

A. Alex and a Rhombus

While playing with geometric figures Alex has accidentally invented a concept of a n-th order rhombus in a cell grid.

A 1-st order rhombus is just a square 1×1 (i.e just a cell).

A n-th order rhombus for all n≥2 one obtains from a n−1-th order rhombus adding all cells which have a common side with it to it (look at the picture to understand it better).

Alex asks you to compute the number of cells in a n-th order rhombus.

Input

The first and only input line contains integer n (1≤n≤100) — order of a rhombus whose numbers of cells should be computed.

Output

Print exactly one integer — the number of cells in a n-th order rhombus.

Examples

input

1

output

1

input

2

output

5

input

3

output

13

Note

Images of rhombus corresponding to the examples are given in the statement.

思路：感觉是找规律题，推一下找找规律就好了......

 1 #include<iostream>
 2 #include<cstring>
 3 #include<cstdio>
 4 #include<cmath>
 5 #include<algorithm>
 6 #include<map>
 7 #include<set>
 8 #include<vector>
 9 #include<queue>
10 using namespace std;
11 #define ll long long 
12 const int mod=1e9+7;
13 const int inf=1e9+7;
14 
15 //const int maxn=
16 
17 int main()
18 {
19     ios::sync_with_stdio(false);cin.tie(0);cout.tie(0);
20     
21     int n;
22     
23     while(cin>>n)
24     {
25         int ans=0;
26         
27         int f=(n<<1)-1;
28         
29         ans+=f;
30         
31         f-=2;
32         
33         while(f!=-1)
34         {
35             ans+=(f<<1);
36             f-=2;
37         }
38         
39         cout<<ans<<endl;
40         
41     }
42     
43     return 0;
44 }

标签：569,Alex,int,Codeforces,rhombus,th,input,include,order
来源： https://www.cnblogs.com/xwl3109377858/p/11070269.html