题解

#include<iostream>
using namespace std;
int n , daan , sum=1;
int main(){
	cin>>n;
	while(true){
		for(int j=1;j<=sum;j++){
			daan = daan + sum;
			n--;
			if(n == 0){
				cout << daan << endl;;
				return 0;
			}
		}
		sum++;
	}
	return 0;
}