#include <bits/stdc++.h>

using namespace std;

#define ll 			long long
#define db			double
#define up(i,j,n)		for (int i = j; i <= n; i++)
#define down(i,j,n)	for (int i = j; i >= n; i--)
#define cadd(a,b)		a = add (a, b)
#define cpop(a,b)		a = pop (a, b)
#define cmul(a,b)		a = mul (a, b)
#define pr			pair<int, int>
#define fi			first
#define se			second
#define SZ(x)		(int)x.size()
#define bin(i)		(1 << (i))
#define Auto(i,node)	for (int i = LINK[node]; i; i = e[i].next)

template<typename T> inline void cmax(T & x, T y){y > x ? x = y : 0;}
template<typename T> inline void cmin(T & x, T y){y < x ? x = y : 0;}

ll calc(ll n){
	return n * n;
}

int main(){
	ll n;
	scanf("%lld", &n);
	printf("%lld\n", calc((n + 1) * n / 2) - calc((n - 1) * n / 2));
	return 0;
}