수들의 합

www.acmicpc.net/problem/1789

1789번: 수들의 합

#include <iostream>
#include <algorithm>
#include <string>
#include <deque>
#include<cstring>
#include<map>

using namespace std;


int main() {
	
	long long s;
	cin >> s; 
	
	long long answer = 0;

	long long i = 1;
	long long  sum = 0;
	
	while (sum <= s) {

		if (sum == s) { cout << i - 1 << endl; return 0; }
		sum += i;
		i++;
	}

	answer = i - 2;

	
	cout << answer<<endl;



}