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

#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 | | --- | --- | --- | | | | | | | | |

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<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;

}