Go: package main

import (
        "fmt"
)

func main() {
        var num int
        for {
                _, err := fmt.Scan(&num)
                if err != nil {
                        break
                } else {
                        fmt.Printf("%d\n", (num*num+num+2)/2)
                }
        }
}

C++: #include <iostream>
#include <vector>
#include <stack>
#include <queue>
#include <map>
#include <bitset>
#include <algorithm>
#include <cstdio>
#include <cstdlib>
#include <cmath>
#include <cstring>

#define X first
#define Y second
using namespace std;

int main(){
	int n = 0;
	while(cin >> n){
		int sum = 1;
		if(cin.eof()) break;
		for(int i = 1; i <= n; i++){
			sum += i;
		}
		cout << sum << endl;
	}
	return 0;
}

C++: //#define _GRIBCXX_DEBUG
#include <algorithm>
#include <cctype>
#include <climits>
#include <cmath>
#include <complex>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <ctime>
#include <deque>
#include <functional>
#include <iostream>
#include <iomanip>
#include <list>
#include <map>
#include <memory>
#include <numeric>
#include <queue>
#include <set>
#include <stack>
#include <string>
#include <utility>
#include <vector>
using namespace std;


// ?????¬???????????¬??????
#pragma region MACRO
#define P(x) cout << (x) << endl
#define p(x) cout << (x)
#define PED cout << "\n"
#define rep(i,n) for(int i=0; i<(int)n; ++i)
#define REP(i,x,n) for(int i=x; i<(int)n; ++i)
#define repi(i,n) for(int i=0; i<=(int)n; ++i)
#define REPI(i,x,n) for(int i=x; i<=(int)n; ++i)
#define ILP while(true)
#define FOR(i,c) for(__typeof((c).begin())!=(c).begin(); i!=(c).end(); ++i)
#define ALL(c) (c).begin(), (c).end()
#define mp make_pair
#pragma endregion

// ???
#pragma region TYPE_DEF
typedef long long ll;
typedef pair<int, int> pii;
typedef pair<string, string> pss;
typedef pair<string, int> psi;
typedef pair<int, string> pis;
typedef vector<int> vi;
typedef vector<double> vd;
typedef vector<long> vl;
typedef vector<long long> vll;
typedef vector<string> vs;
#pragma endregion

// Effective std
#pragma region ESTD
template<typename C, typename T>
constexpr int count(C& c, T t) { return count(ALL(c), t); }
template<typename C, typename F>
constexpr int count_if(C& c, F f) { return count_if(ALL(c), f); }
template<typename C, typename T>
void erase(C& c, T t) { remove(ALL(c), t), c.end(); }
template<typename C>
void remove(vector<C>& c, unsigned int index) { c.erase(c.begin()+index); }
template<typename C, typename T, typename U>
constexpr void replace(C& c, T t, U u) { replace(ALL(c), t, u); }
template<typename C, typename F, typename U>
constexpr void replace_if(C& c, F f, U u) { (ALL(c), f, u); }
template<typename C>
constexpr void reverse(C& c) { reverse(ALL(c)); }
template<typename C>
constexpr void sort(C& c) { sort(ALL(c)); }
template<typename C, typename Pred>
constexpr void sort(C& c, Pred p) { sort(ALL(c), p); }
#pragma endregion

// ?????°
#pragma region CONST_VAL
#define PI (2*acos(0.0))
#define EPS (1e-9)
#define MOD (int)(1e9+7)
#pragma endregion


int main()
{
    int n;
    while(cin>>n) {
        int ans = 1;
        for(int i=n; i>0; i--) ans+=i;
        P(ans);
    }
    return 0;
}

C++: #include<iostream>
using namespace std;

int main(){
  int a[50];
  for(int i=0;i<50;i++){
    cin >> a[i];
  }
  for(int i=0;i<50;i++){
  cout << 1/2*a[i]*(a[i]+1)+1 <<endl;
  }
  return 0;
}

C++: #include<iostream>
using namespace std;

int main(){
  int n;
  while(cin>>n){
  cout << (1/2)*n*(n+1)+1 <<endl;
  }
  return 0;
}

C++: #include <iostream>
#include <stdio.h>

using namespace std;

int main(void){
  int a_1 = 2;
  int x;
  int s;
  cin >> x;

  while(scanf("%d", &x) != EOF ){
    if(x == 1){
      cout << a_1;
    }else{
      s += a_1;
      for(int i = 1; i <= x; i++){
        s += i;
      }
    }
  }

}

C++: #include <iostream>
#include <algorithm>
#include <map>
#include <set>
#include <queue>
#include <stack>
#include <numeric>
#include <bitset>
#include <cmath>

static const int MOD = 1000000007;
using ll = long long;
using u32 = unsigned;
using u64 = unsigned long long;
using namespace std;

template<class T> constexpr T INF = ::numeric_limits<T>::max()/32*15+208;

int main() {
    int n;
    while(cin >> n){
        cout << n*(n+1)/2 +1 << "\n";
    }
    return 0;
}

C++: i,a;main(n){for(;i=~scanf("%d",&n);printf("%d\n",a))for(i=a=1;i<=n;)a+=i++;}

C++: #include<iostream>
using namespace std;

int NumofArea(int n){
  if(n == 1) return 2;
  else return n + NumofArea(n-1);
}

int main(){
  int n;
  while(cin >> n){
      int ans = NumofArea(n);
      cout << ans << endl;
  }
}

C++: #include<iostream>int main(){for(int n;std::cin>>n;)std::cout<<n*(n+1)/2+1<<std::endl;}

C++: #include <iostream>
using namespace std;

#define MAX_N 10001

int main()
{
	int seq[MAX_N];
	int a=1;
	for(int i=0;i<MAX_N;i++){
		seq[i] = a;
		a += i + 1;
	}
	
	int n;
	while(cin>>n){
		cout<<seq[n]<<endl;
	}
	return 0;
}

C++: #include <stdio.h>
#define rep(i, n) for (int i = 0; i < (int)(n); i++)

int ans[12000];

int main() {
    ans[0] = 1;
    rep (i, 10000) ans[i+1] = ans[i]+i+1;
    int n;
    while (scanf("%d", &n) != EOF) printf("%d\n", ans[n]);
    return 0;
}

C++: #include <iostream>

using namespace std;

int main()
{
	for(int n;cin>>n;)
		cout<<1+n*(n+1)/2<<endl;
	
	return 0;
}

C++: #include<iostream>

using namespace std;

int main(void)
{
	while(1)
	{
		int n;
		if(!(cin>>n))break;
		cout<<1+n*(n+1)/2<<endl;
	}
}

C++: #include <cstdio>
#include <iostream>
using namespace std;

int max_area(int n)
{
  if (n == 1) return (2);
  else return ((n - 1) + n); // ??????????????¨?????¢??°+????????§???????????¬??°
}
int main()
{
  int n;

  while (~scanf("%d", &n)){
    printf("%d\n", max_area(n));
  }

  return (0);
}

C++: #include <iostream>
#include <vector>

using namespace std;

typedef long long ll;
//int main(){
//    vector<ll> vec(10001);
//    vec.push_back(1);
//    for(int i=1;i<=10000;i++){
//        vec[i] = vec[i-1] + i;
//    }
//    int n;
//    while(cin >> n){
//        cout << vec[n] << endl;
//    }
//    return 0;
//}

 int main(){
     int n;
     while(cin >> n){
         cout << n*(n-1)/2 +1 << endl;
     }
     return 0;
 }

C++: #include<iostream>
using namespace std;


int pie(int x) {
	int y=x*(x + 1) / 2;
	return y;
}

int main() {
	int a;
	int sum = 0;
	while (cin >> a) {
		int sum = pie(a);
		sum += 1;
		cout << sum << endl;
		sum = 0;
	}
	return 0;
}

C++: #include<iostream>
#include<cstdio>
#include<string>

using namespace std;

int main()
{	
	int ans[10001]={0};
	int n;
	ans[1]=2;
	for(int i=2;i<=10001;i++){
		ans[i]=ans[i-1]+i;
	}
	while(cin>>n){
		cout<<ans[n]<<endl;
	}
	return 0;
}

C++: #include <iostream>
#include <iomanip>
#include <vector>
#include <string>
#include <stack>
#include <queue>
#include <deque>
#include <set>
#include <map>
#include <algorithm>
#include <sstream>
#include <cstdlib>
#include <cstring>
#include <functional>
#include <numeric>
#include <cmath>
#include <climits>
#include <limits>
#include <cfloat>
#include <fstream>
using namespace std;

int main()
{
//	cut here before submit 
//	freopen("testcase.area", "r", stdin);
	string str = "";
	while (getline (cin, str ) ){
		if (str.empty() ){
			break;
		} // end if
		int n;
		stringstream ss(str);
		ss >> n;
		int res = n*(n+1)/2 + 1;

		cout << res << endl;
	} // end loop
		
	return 0;
}

C++: #include<iostream>

using namespace std;

int main(){
	int n;
	while(cin>>n){
		n=(n*n+n+2)/2;
		cout<<n<<endl;
	}
}

C++: #include <string>
#include <cstdio>
#include <cstring>
#include <cmath>
#include <vector>
#include <queue>
#include <set>
#include <utility>
#include <algorithm>
#include <numeric>
#include <iostream>
#include <iterator>
#include <sstream>

using namespace std;

int main()
{
	int n;
	while(cin>>n){
		cout << 1 + n * (n + 1) / 2 << endl;
	}
	return 0;
}

C++: #include <iostream>
int main()
{
    int n;
    while (std::cin >> n) {
	n--;
	std::cout << (n * n + 3 * n + 4) / 2 << std::endl;
    }
}