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++: //The Number of Area
#include<bits/stdc++.h>
using namespace std;

long long table[10001];

int main(){
  int n;
  table[0]=1;
  for(int i=1; i<=10000; i++)
    table[i]=table[i-1]+i;
  while(cin>>n){
    cout<<table[n]<<endl;
  }
  return 0;
}

C++: #include <algorithm>
#include <bitset>
#include <cassert>
#include <cctype>
#include <climits>
#include <cmath>
#include <complex>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <ctime>
#include <deque>
#include <functional>
#include <iostream>
#include <iterator>
#include <list>
#include <map>
#include <numeric>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <utility>
#include <vector>
using namespace std;

#define dump(a) (cerr << (#a) << " = " << (a) << endl)
#define FOR(it,c) for(__typeof((c).begin())it=(c).begin(); it!=(c).end();++it)
#define RFOR(it,c) for(__typeof((c).rbegin())it=(c).rbegin(); it!=(c).rend();++it)
#define exist(c, v) (find((c).begin(), (c).end(), (v)) != (c).end())

template<class T> inline void chmax(T& a, const T& b) { if(b > a) a = b; }
template<class T> inline void chmin(T& a, const T& b) { if(b < a) a = b; }

template<typename T, typename U> ostream& operator<<(ostream& os, const pair<T, U>& p) {
	os << '(' << p.first << ", " << p.second << ')';
	return os;
}

template<typename T> ostream& operator<<(ostream& os, const vector<T>& v) {
	copy(v.begin(), v.end(), ostream_iterator<T>(os, " "));
	return os;
}

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

	const int MAX = 10000;
	vector<int> cnt(MAX + 1, 1);
	for(int i = 1; i <= MAX; ++i)
		cnt[i] = cnt[i - 1] + i;

	for(int n; scanf("%d", &n) == 1;)
		printf("%d\n", cnt[n]);

	return EXIT_SUCCESS;
}

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

using namespace std;
 
int main(void){

	int n;
	int ans[10001];
	ans[1]=2;

	for(int i=2;i<=10000;i++){
		ans[i]=ans[i-1]+i;
	}

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

    return 0;
}

C++: #include<iostream>
using namespace std;
int a;
int main() {
	while (cin >> a) {
		cout << a*(a + 1) + 1 << 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>
#include<string>
using namespace std;

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

	return 0;
}

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

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

C++: #include <iostream>

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

    int n;

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

    return 0;
}

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

int main(){

  long long int a,n;

  while(cin >> n){

    for(int i=1;i<=n;i++){
      if(i == 1) a = 2;
      else a += i;
    }

    if(n == 0) cout << 0 << endl;
    else cout << a << endl;
  }
}

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

int main(){
  int n;
  while(cin >> n){
  cout << (int) (n*n + n + 2) * 0.5 << endl;
  }
  return 0;
}

C++: #include<iostream>
using namespace std;
int main(){
  int i,n,d[10005]={};
  d[0]=1;
  for(i=0;i<10000;i++) d[i+1]=d[i]+i+1;
  while(cin>>n)
    cout << d[n] << endl;
  return 0;
}

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

int main(){
	int n;
	while(cin>>n){
		long int ans = 0;
		for(int i =0;i<=n;i++){
			ans += i;
		}
		cout << ans << 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) {
		for (int i = 0; i < a; i++) {
			int func = pie(i);
			++func;
			sum += func;
		}
		cout << sum << endl;
		sum = 0;
	}
	return 0;
}

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

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

C++: #include<iostream>

using namespace std;

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

}

C++: #include <iostream>
using namespace std;
int main(){
  int n, i, s;
  int a[1000];
  a[0]=2;
  for(i=1; i<1000;i++){
    a[i]=a[i-1]+i+1;  
  }
  while(cin>>n){
  cout<<a[n-1];
  }
  return 0;  
}

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

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

C++: #include <iostream>

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

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

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

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

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

C++: #include <set>
#include <map>
#include <list>
#include <queue>
#include <stack>
#include <cmath>
#include <ctype.h>
#include <ctime>
#include <cstdio>
#include <vector>
#include <string>
#include <bitset>
#include <cctype>
#include <cstdlib>
#include <cstring>
#include <utility>
#include <numeric>
#include <complex>
#include <sstream>
#include <fstream>
#include <iomanip>
#include <cassert>
#include <iostream>
#include <iterator>
#include <algorithm>

using namespace std;

#define REP(i, x, n) for(int i = x; i < n; i++)
#define rep(i, n) REP(i, 0, n)
#define lengthof(x) (sizeof(x) / sizeof(*(x)))
#define FILL(ptr, value) FILL_((ptr), sizeof(ptr)/sizeof(value), (value))
template <typename T>
void FILL_(void * ptr, size_t size, T value){
  std::fill((T*)ptr, (T*)ptr+size, value);
}
//4方向ベクトル→↑←↓
int dx[] ={1,0,-1,0};
int dy[] ={0,-1,0,1};
int dp[10010];
int main()
{
  int n;
  dp[0] = 1;
  for(int i = 1;i < 10010;i++){
    dp[i] =dp[i-1]+i;
  }
  while(cin>>n){
    cout <<dp[n]<<endl;
  }
  return 0;
}

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

int main(){
	int a;
	while (cin >> a){
		int ans = 1;
		for (int i = 1; i <= a; i++){
			ans += i;
		}
		cout << ans << endl;
	}
}

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

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

C++: #include <vector>
#include <list>
#include <map>
#include <set>
#include <deque>
#include <stack>
#include <bitset>
#include <algorithm>
#include <functional>
#include <numeric>
#include <utility>
#include <sstream>
#include <iostream>
#include <iomanip>
#include <cstdio>
#include <cmath>
#include <cstdlib>
#include <cctype>
#include <string>
#include <cstring>
#include <ctime>
#include <queue>

using namespace std;
using ull = unsigned long long;
using ll = long long;
using lli = long long int;
using ld = long double;
using pa = pair<int,int>;
#define SORT(v, n) sort(v, v+n);
#define VSORT(v) sort(v.begin(), v.end());
#define GRESORT(v) sort(v.begin(),v.end(),greater<int>())
#define REVERSE(v) reverse(v.begin(),v.end())
#define overlap(v) v.erase(unique(v.begin(),v.end()),v.end())
#define debug(x) cout << #x << ": " << x << endl
#define FOR(i,a,b) for(int i = (a); i < (b); i++)
#define rep(i,n) FOR(i,0,n)
#define RFOR(i,a,b) for(int i = (b-1); i >= a; i--)
#define rrep(i,n) RFOR(i,0,n)
#define INF 999999999

//4??????
//int dy[]={0, 0, 1, -1};
//int dx[]={1, -1, 0, 0};

//8??????
//int dy[]={0,0,1,-1,1,1,-1,-1};
//int dx[]={1,-1,0,0,1,-1,1,-1};

ll mod = (ll)1e9+7;

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

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

    solve();

    return 0;
}