#include <bits/stdc++.h>
#define rep(i,n) for(int i = 0; i < (n); ++i)
#define srep(i,s,t) for (int i = s; i < t; ++i)
#define drep(i,n) for(int i = (n)-1; i >= 0; --i)
using namespace std;
typedef long long int ll;
typedef pair<int,int> P;
#define yn {puts("YES");}else{puts("NO");}
#define MAX_N 200005
int dx[5] = {-1, -1, 1, 1, -1};
int dy[5] = {-1, 1, -1, 1, 0};
int main() {
    ll n; cin >> n;
    ll ans = 4 * n * (n+1) / 2 + 1 + 4 * (n-1) * n / 2 + 1;
    cout << ans << endl;
    return 0;
}