#include <bits/stdc++.h>
using namespace std;
bool Check(unsigned int N, int pos) { return (bool)(N & (1LL << pos)); }
long long Set(unsigned int N, int pos) { return N = N | (1LL << pos); }
int dx[8] = {0, 0, 1, -1, -1, 1, 1, -1};
int dy[8] = {1, -1, 0, 0, 1, -1, 1, -1};
bool chk(int x, int pos) { return (bool)(x & (1 << pos)); }
int Set(int x, int pos) { return x = x | (1 << pos); }
int clr(int x, int pos) { return x = x & ~(1 << pos); }
int n, m, a[100005];
int main() {
  int ii, i, j, k, z = 0, c = 0, t, x, y, l, r, mid;
  scanf("%d", &n);
  cout << n * n + (n - 1) * (n - 1) << endl;
}
