913 - Joana and the Odd Numbers/913.cpp

   1 /*
   2   Problem:
   3   Andrés Mejía-Posada (andmej@gmail.com)
   4  */
   5 using namespace std;
   6 #include <algorithm>
   7 #include <iostream>
   8 #include <iterator>
   9 #include <sstream>
  10 #include <fstream>
  11 #include <numeric>
  12 #include <cassert>
  13 #include <climits>
  14 #include <cstdlib>
  15 #include <cstring>
  16 #include <string>
  17 #include <cstdio>
  18 #include <vector>
  19 #include <cmath>
  20 #include <queue>
  21 #include <deque>
  22 #include <stack>
  23 #include <list>
  24 #include <map>
  25 #include <set>
  26
  27 #define foreach(x, v) for (typeof (v).begin() x = (v).begin(); x != (v).end(); ++x)
  28 #define For(i, a, b) for (int i=(a); i<(b); ++i)
  29 #define D(x) cout << #x " is " << x << endl
  30
  31 int main(){
  32   long long n;
  33   while (cin >> n){
  34     long long i = (n-1)*(n-1)/4 + n - 3;
  35     cout << 6*i + 9 << endl;
  36   }
  37   return 0;
  38 }