[백준] 8393번 : 합 - C++

https://www.acmicpc.net/problem/8393

#include <iostream>

using namespace std;

int main() {
    int n;
    cin >> n;
    int sum=0;
    if(n%2==1){
        int m=(n+1)/2;
        sum=(1+n)*(n/2)+m;
    }
    else sum=(1+n)*((n+1)/2);
    cout << sum;
}