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>
using namespace std;

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

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

C++: #include <iostream>
#include <string>
#include <math.h>
using namespace std;

int main()
{
	double n;
	int area;
	while (cin >> n)
	{
		area = (pow(n,2.0) + n + 2) / 2;		//area = 1 + n(1+n)/2
		cout << area << endl;
	}
	return 0;
}

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

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

int main()
{
 int x, m ,count;
 while(cin>>n)
 {
  if(n>2)
  {
    for(int i=0; i<n-2; i++)
     {
        m+=count;
        count++;
      }
     cout<<n*2+m<<endl;
    }
   else
   {
    cout<<n*2<<endl;
   }
   }
  return 0;
}

C++: #include <iostream>

using namespace std;

int main(){
	int n;
	while(cin >> n){
		int ans = 2;
		for(int i = 2;i <= n;i++){
			ans += i;
		}
		cout << ans << endl;
		}
		}

C++: #include<iostream>

int main()
{
	int n;

	while(std::cin >> n)
	{
		std::cout << (n*n+n+2)/2 << '\n';
	}
	
}

C++: #include<bits/stdc++.h>
using namespace std;

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

C++: #include <iostream>

using namespace std;

void solve()
{
	int n;
	while(cin >> n)
	{
		int ans = 1;
		for(int i = 1; i <= n; ++i)
		{
			ans += i;
		}
		cout << ans << endl;
	}
}

int main()
{
	solve();
	return(0);
}

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

int main(){
    int n;
    while(scanf("%d",&n) != EOF){
        cout << 1+(n+1)*n/2 << endl;
    }
}

C++: #include <stdio.h>

int main(void)
{
	int n;
	while(scanf("%d",&n) != EOF){
		printf("%d\n",n * (n + 1) / 2 + 1);
	}
	return 0;
}

C++: #include<bits/stdc++.h>
using namespace std;

int main(){
int a[10010];
a[0]=1;
a[1]=2;
for(int i=2;i<10010;i++){
a[i]=a[i-1]+i;
}



int n;
while(cin>>n){
cout<<a[n]<<endl;
}
return 0;
}

C++: #include<cstdio>
main(){for(int n;~scanf("%d",&n);printf("%d\n",n*(n+1)/2+1));}

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

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

C++: #include <vector>
#include <map>
#include <set>
#include <stack>
#include <queue>
#include <algorithm>
#include <utility>
#include <functional>
#include <sstream>
#include <iostream>
#include <cstdio>
#include <cmath>
#include <cstdlib>
#include <cctype>
#include <string>
#include <cstring>
#include <ctime>
#include <climits>
using namespace std;
inline int toInt(string s) { int v; istringstream sin(s); sin >> v; return v;}
template<class T> inline string toStr(T x) { ostringstream sout; sout << x; return sout.str();}
typedef vector<int> vi;
typedef vector<vi>  vvi;
typedef vector<string> vs;
typedef pair<int, int> pii;
typedef long long ll;
#define ALL(a) (a).begin(),(a).end()
#define RALL(a) (a).rbegin(),(a).rend()
#define FOR(i,a,b) for(int i=(a);i<=(b);++i)
#define REP(i,n) FOR(i,0,(n)-1)
const double EPS = 1e-12;
const double PI = acos(-1.0);
const int INF = INT_MAX/10;

int main() {
	vi num(10000+1);
	num[0] = 0;
	num[1] = 2;
	FOR(i, 2, 10000) {
		num[i] = num[i-1]+i;
	}
	
	int n;
	while(cin >> n) {
		cout << num[n] << endl;
	}

	return 0;
}

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

int main()
{
	int a[10001];
	a[0] = 0;
	a[1] = 2;
	for(int i=2;i<10001;i++)
	{
		a[i] = a[i-1] + i;
	}

	int n;
	while(cin >> n)
	{
		cout << a[n] << endl;
	}
	return 0;
}

C++: #include <bits/stdc++.h>
using namespace std;

int main(){
  int n, x;

  while(cin>>n){
    for(int i = 0; i < n; ++i){
      x += (2 + i);
    }
    cout << x << endl;
    
  }
    
  return 0;
}

C++: #include<stdio.h>
int main(void)
{
	int a,s,d,i;
	while(scanf("%d",&a)!=EOF){
	s=1;
	for(i=1;i<=a;i++){
		s=s+i;
	}
	printf("%d\n",s);
	}
	return 0;
}

C++: #include <bits/stdc++.h>

#define rep(i, n) for (int i = 0; i < int(n); i++)
#define rrep(i, n) for (int i = int(n) - 1; i >= 0; i--)
#define reps(i, n) for (int i = 1; i <= int(n); i++)
#define rreps(i, n) for (int i = int(n); i >= 1; i--)
#define repc(i, n) for (int i = 0; i <= int(n); i++)
#define rrepc(i, n) for (int i = int(n); i >= 0; i--)
#define repi(i, a, b) for (int i = int(a); i < int(b); i++)
#define repic(i, a, b) for (int i = int(a); i <= int(b); i++)
#define repp(i, n) rep(i, n)
#define reppp(i, n) repp(i, n)
#define rrepp(i, n) rrep(i, n)
#define repss(i, n) reps(i, n)
#define repcc(i, n) repc(i, n)
#define repii(i, a, b) repi(i, a, b)
#define each(x, y) for (auto &x : y)
#define all(a) (a).begin(), (a).end()
#define bit(b) (1ll << (b))

using namespace std;

using i32 = int;
using i64 = long long;
using u64 = unsigned long long;
using f80 = long double;
using vi32 = vector<i32>;
using vi64 = vector<i64>;
using vu64 = vector<u64>;
using vf80 = vector<f80>;
using vstr = vector<string>;

inline void yes() { cout << "Yes" << '\n'; exit(0); }
inline void no() { cout << "No" << '\n'; exit(0); }
inline i64 gcd(i64 a, i64 b) { if (min(a, b) == 0) return max(a, b); if (a % b == 0) return b; return gcd(b, a % b); }
inline i64 lcm(i64 a, i64 b) { return a / gcd(a, b) * b; }
inline u64 xorshift() { static u64 x = 88172645463325252ull; x = x ^ (x << 7); return x = x ^ (x >> 9); }
void solve(); int main() { ios::sync_with_stdio(0); cin.tie(0); cout << fixed << setprecision(16); solve(); return 0; }
template <typename T> class pqasc : public priority_queue<T, vector<T>, greater<T>> {};
template <typename T> class pqdesc : public priority_queue<T, vector<T>, less<T>> {};
template <typename T> inline void amax(T &x, T y) { if (x < y) x = y; }
template <typename T> inline void amin(T &x, T y) { if (x > y) x = y; }
template <typename T> inline T power(T x, i64 n, T e = 1) { T r = e; while (n > 0) { if (n & 1) r *= x; x *= x; n >>= 1; } return r; }
template <typename T> istream& operator>>(istream &is, vector<T> &v) { each(x, v) is >> x; return is; }
template <typename T> ostream& operator<<(ostream &os, vector<T> &v) { rep(i, v.size()) { if (i) os << ' '; os << v[i]; } return os; }
template <typename T, typename S> istream& operator>>(istream &is, pair<T, S> &p) { is >> p.first >> p.second; return is; }
template <typename T, typename S> ostream& operator<<(ostream &os, pair<T, S> &p) { os << p.first << ' ' << p.second; return os; }

void solve() {
  int n;
  while (cin >> n) {
    i64 ans = 1;
    reps(i, n) ans += i;
    cout << ans << '\n';
  }
}

C++: #include<iostream>
using namespace std;
int main(){
int x;
while(cin>>x){
cout<<x*(x-1)/2<<endl;
}
return 0;
}

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

int main(){
	int n;
	while(cin >> n && n){
		int sum = 2;
		int piyo = 2;
		for(int i=1; i<n; ++i){
			sum += piyo;
			piyo++;
		}
		cout << sum;
	}
	return 0;
}

C++: #include<iostream>
using namespace std;
int ans(int a){
	if(a==1) return 2;
	return a+ans(a-1);
}
int main(){
	int n;
	while(){
		cout<<ans(n)<<endl;
	}
	return 0;
}

C++: #include <cstdio>

int line[10000];

int rec(int n){
	if(line[n] != -1) return line[n];
	if(n == 1) return line[n] = 2;
	return line[n] = rec(n-1) + n;
}
int main(){
	int n;
	for(int i = 0; i < 10000; i++) line[i] = -1;
	while(scanf("%d", &n) != EOF){
		printf("%d\n", rec(n));
	}
	return 0;
}