#include <bits/stdc++.h>
using namespace std;
int s=1;
int ss(int n){
	if(s>=5000){
		return s;	
	}
	else{
		s+=n;
		n++;
		ss(n);
	}
	
}
int main(){
	cout<<ss(1);
	return 0;
	}

/**************************************************************
	Problem: 1146
	User: fzy001
	Language: C++
	Result: Wrong Answer
****************************************************************/