#include<bits/stdc++.h>
using namespace std;
//      std macros
typedef long long ll;
typedef pair<int ,int> pii;
typedef pair<ll ,ll> pll;
//      dereference
#define F first
#define S second
#define pb push_back
#define mp make_pair
//      loops
#define rep(i,n) for(int i=0;i<n;++i)
#define REP(i,a,b) for(int i=a;i<=b;++i)
#define PER(i,b,a) for(int i=b;i>=a;--i)
#define all(X) (X).begin(), (X).end()
//      I/O
#define sd(n) scanf("%d",&n)
#define sd2(x,y) scanf("%d%d",&x,&y)
#define sd3(x,y,z) scanf("%d%d%d",&x,&y,&z)
#define sll(n) scanf("%lld",&n)
#define sll2(x,y) scanf("%lld%lld",&x,&y)
#define sll3(x,y,z) scanf("%lld%lld%lld",&x,&y,&z)
#define ss(s) scanf("%s",s)
//      debug
#define debug(x) cerr<<"debug->"<<#x<<"::"<<x<<endl
#define debug2(x,y) cerr<<#x<<" :: "<<x<<"\t"<<#y<<" :: "<<y<<"\n"
#define debug3(x,y,z) cerr<<#x<<" :: "<<x<<"\t"<<#y<<" :: "<<y<<"\t"<<#z<<" :: "<<z<<"\n"
#define debug4(x,y,z,w) cerr<<#x<<" :: "<<x<<"\t"<<#y<<" :: "<<y<<"\t"<<#z<<" :: "<<z<<"\t"<<#w<<" :: "<<w<<"\n"
//      set values
#define mset(n,k) memset(n,k,sizeof(n))
//modular expo
ll power(ll a,ll b, ll c){
    ll x=1,y=a;
    while(b>0){
        if(b&1)
            x=(x*y)%c;
        y=(y*y)%c;
        b/=2;
    }
    return x%c;
}
int dx[]={0,-1,0,1};
int dy[]={-1,0,1,0};//clockwise from left
int dr[]={1,1,0,-1,-1,-1, 0, 1};
int dc[]={0,1,1, 1, 0,-1,-1,-1};//anticlockwise from down
int main() {

	ll k;
	sll(k);
	ll idx = (k*(k-1))/2 + 1;
	ll fi = 1+(idx-1)*2;
	ll sum = (k*(2*fi+(k-1)*2))/2;
	printf("%lld\n",sum);
	
	
	return 0;
}