#include <iostream>
using namespace std;
int main(){
    int a=0,n;
    cin>>n;
    for(int i=1;i<=n;i++){
    	a=a+i;
	}
	cout<<a;
    return 0;
}

一次过

#include <algorithm>
#include <bitset>
#include <cctype>
#include <cerrno>
#include <clocale>
#include <cmath>
#include <complex>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <ctime>
#include <cwchar>
#include <cwctype>
#include <complex.h>
#include <deque>
#include <exception>
#include <fstream>
#include <functional>
#include <fenv.h>
#include <iomanip>
#include <ios>
#include <iosfwd>
#include <iostream>
#include <istream>
#include <inttypes.h>
#include <limits>
#include <list>
#include <map>
#include <ostream>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <stdexcept>
#include <streambuf>
#include <string>
#include <stdbool.h>
#include <stdint.h>
#include <tgmath.h>
#include <utility>
#include <vector>
using namespace std;
#define LL long long
const int N = 1e5 + 10;
const int INF = 0x3f3f3f3f;

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

#include<bits/stdc++.h> using namespace std; int main() {
int n; cin>>n; cout<<(1+n)*n/2; return 0; }

#include #include #include using namespace std; int n , sum; int main() {

cin>>n;
for(int i = 1 ; i <= n; i++)
{
  sum += i;	
}	
cout << sum;
return 0;

}

#include <bits/stdc++.h>
 using namespace std; 
int n;
int main()
{
cin>>n;
cout<<(1+n)*n/2;
}

还行

#include using namespace std; int n,ans; int main() { cin>>n; for(int i=1;i<=n;i++) { ans += i; } cout <<ans; return 0; }

#include<iostream>
using namespace std;
int main(){
	long long n;
	cin>>n;
	cout<<(1+n)*n/2;
}

一个字符都不想多打了

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

| col1

| col2 | col3 | | --- | --- | --- | | | | | | | | |

#include<iostream>
using namespace std;
int main(){
	long long n;
	cin>>n;
	cout<<(1+n)*n/2;
}

#include

using namespace std;

int main(){

int a;

cin >> a;

a = (1 + a) * a / 2;

cout << a << endl;

}