第一个题解+第一个AC

#include <iostream>
using namespace std;
int main(){
    int n;
    cin >> n;
    int gold = 1, r = 1;
    int sum = 0;
    for(int i = 1; i <= n; i++){
        sum += gold;
        if(r == gold){
            gold++;
            r = 1;
            continue;
        }else{
            r++;
        }
    }
    cout << sum;
    return 0;
}