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 <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>
#include <string>
#include <vector>
#include <deque>
#include <queue>
#include <algorithm>
#include <iomanip>
#include <set>
#include <map>
#include <bitset>
#include <cmath>
#include <functional>

using namespace std;

#define REP(i,n) for(ll (i) = (0);(i) < (n);++i)
#define REV(i,n) for(ll (i) = (n) - 1;(i) >= 0;--i)
#define PB push_back
#define EB emplace_back
#define MP make_pair
#define FI first
#define SE second
#define SHOW1d(v,n) {REP(WW,n)cerr << v[WW] << ' ';cerr << endl;}
#define SHOW2d(v,WW,HH) {REP(W_,WW){REP(H_,HH)cerr << v[W_][H_] << ' ';cerr << endl;}}
#define ALL(v) v.begin(),v.end()
#define Decimal fixed<<setprecision(20)
#define INF 1000000000
#define LLINF 1000000000000000000LL
#define MOD 998244353

typedef long long ll;
typedef pair<ll,ll> P;

int main(){
	cin.tie(0);cout.tie(0);ios::sync_with_stdio(false);

	ll n;
	while(cin >> n){
		cout << 1 + n * (n + 1) / 2 << endl;
	}

	return 0;
}

C++: #include <iostream>
#include <iomanip>
#include <cstdio>
#include <vector>
#include <map>
#include <cmath>
#include <algorithm>
#include <string>
#define shosu(x) fixed<<setprecision(x)
using namespace std;
typedef pair<int,int> P;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef pair<int,P> pip;
typedef long long ll;
const int inf=1<<30;
const double pi=acos(-1);

int n;

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

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

using namespace std ;

#define pb(n) push_back(n)
#define fi first
#define se second
#define np string::npos
#define all(r) (r).begin(),(r).end()
#define gsort(st,en) sort((st),(en),greater<int>())
#define vmax(ary) *max_element(all(ary))
#define vmin(ary) *min_element(all(ary))
#define debug(x) cout<<#x<<": "<<x<<endl

#define rep(i,n) for(int i = 0; i < (int)(n);++i)
#define repc(i,a,b) for(int i = (a);i < (int)(b);++i)
#define repi(it,array) for(auto it = array.begin(),end = array.end(); it != end;++it)
#define repa(n,array) for(auto n :(array))

typedef long long ll ;
typedef vector<int> vi ;
typedef vector<ll> vl ;
typedef map<string,int> dict;

constexpr int imax = ((1<<30)-1)*2+1 ;
constexpr int inf = 100000000;
double eps = 1e-10 ;

template <typename T>
void out(vector < T > v)
{
  for(size_t i = 0; i < v.size(); i++)
  {
    debug(v[i]);
  }
}

template<typename T>
string ntos( T i ) {
  ostringstream s ;
  s << i ;
  return s.str() ;
}

template<typename T>
T ston(string str, T n){
  istringstream sin(str) ;
  T num ;
  sin >> num ;
  return num ;
}

int main(){
  cin.tie(0);
  ios::sync_with_stdio(false);
  int n,ans;
  while(cin >> n){
    cout << 3*n-2<< endl;
  }
  return 0;
}

C++: #include <stdio.h>

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

C++: #include <iostream>
using namespace std;
int main(void){
  int n;
  int i;
  int ans;
  while(cin>>n){
    ans=n+1;
    for(i=0;i<n;i++){
      ans+=i;
    }
    cout<<ans<<endl;
  }
  return(0);
}

C++: #include<cstdio>
int main(){int n;while(scanf("%d",&n)){printf("%d\n",n*(n+1)/2+1);}return 0;}

C++: #include<bits/stdc++.h>
using namespace std;
int main(){
  int n,a=1;
  while(cin >> n){
    for(int i=1; i<=n; i++){
	a+=i;
    }
  cout << a << endl;
  }
  return 0;
}

C++: #include <cstdio>
int main(void){
  int n;
  while(~scanf("%d",&n)){
    int r = 1;
    for(int i = 1; i <= n; i++){
      r += i;
    }
    printf("%d\n",r);
  }
}

C++: while True:
    try:
        n = int(input())
    except:
        break

    sum = 1
    for i in range(1, n + 1):
        sum += i

    print(sum)

C++: #define _USE_MATH_DEFINES
#include <iostream>
#include <sstream>
#include <cmath>
#include <algorithm>
#include <queue>
#include <stack>
#include <limits>
#include <map>
#include <string>
#include <cstring>

using namespace std;

typedef long long ll;
typedef long double ld;
typedef pair<int,int> P;

int main(){

	int n;
	while(~scanf("%d",&n)){
		int sum=1;
		for(int i=0;i<n;i++){
			sum += i+1;
		}
		cout << sum << endl;
	}
}

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>
using namespace std;
int main()
{
  int n;
  for(;cin>>n;)
    {
      int i=1,a=1;
      for(;i<=n;i++)
	{
	  a+=i;
	}
      cout<<a<<endl;
    }
}

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

int main(){
  int a,sum;
  sum=0;
  cin>>a;
  for(int i=1;i<=a;i++){
  sum=sum+i;}
  cout<<sum+1<<endl;
  return 0;
 }

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

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

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

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

C++: #include "bits/stdc++.h"

#define REP(i,num) for(int i=0;i<(num);++i)
#define ALL(c) c.begin(),c.end()
#define LOOP(i) while(i--)
#define PRINTALL(c) for(auto& x:c){cout<<x<<' ';}cout<<endl;
#define PAIRCOMP(c,comp) [](const pair<ll,ll>& lhs,const pair<ll,ll>& rhs){return lhs.c comp rhs.c;}

using namespace std;
using ll = long long;

constexpr ll atcoder_mod = 1e9+7;

template<typename T=int>
T in(){T x; cin >> x; return (x);}
template<typename T=int,typename C=vector<T>>
C vecin(int N){C x(N);REP(i,N){x[i]=in<T>();}return move(x);}

void vout(){cout << endl;}
template<typename Head,typename... Tail>
void vout(Head&& h,Tail&&... t){cout << ' ' << h;vout(forward<Tail>(t)...);}
void out(){cout << endl;}
template<typename Head,typename... Tail>
void out(Head&& h,Tail&&... t){cout << h;vout(forward<Tail>(t)...);}

int main(){
	cin.tie(0);
	ios::sync_with_stdio(false);

	vector<int> V(10000,0);
	V[0]=2;
	for(int i=1;i<10000;i++){
		V[i] = V[i-1]+i+1;
	}

	int N;
	while(cin>>N){
		out(V[N-1]);
	}
	
	return 0;
}

C++: #include <iostream>
#include <vector>
#include <algorithm>
#include <string>
#include <cstdio>
#include <cmath>
using namespace std;

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

C++: #include<iostream>
using namespace std;
int ans[10001];
int main()
{
	ans[1]=2;
	for(int i = 2; i < 10001; ++i)
	{
		ans[i]=ans[i-1]+i;
	}

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

C++: // 2011/04/02 Tazoe

#include <iostream>
using namespace std;

int main()
{
	while(true){
		int n;
		cin >> n;
		if(cin.eof())
			break;

		cout << n*(n+1)/2+1 << endl;
	}

	return 0;
}

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

// long long int answer[10002];
long long int ans(int in, long long int answer[]){
	if (in == 1){
		answer[in] = 2;
		return answer[1];
	}
	answer[in] = ans(in - 1, answer) + in;
	return answer[in];
}

int main(){
	int in,result;

	// ans(10000, answer);
	while (cin >> in, !cin.eof()){
		result = 1;
		for (int i = 0; i < in; i++){
			// +1, +2, +3,..
			result += (i+1);
		}
		cout << result << endl;
	}

	return 0;
}

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

int main(){
	int n, ans;
	while (cin >> n) {
		ans = 1;
		for (int i = 0; i < n; i++) {
			ans += i+1;
		}
		cout << ans << endl;
	}
	return 0;
}