#include<bits/stdc++.h>
using namespace std;
int he(int n){
    if(n==1) return 1;
    else return he(n-1)+n-1;
}
int s=0,n;
int main(){
    for(int i=1;s<5000;i++){
        s=he(i)+s;
    }
    cout<<s;
 
    return 0;
}
/**************************************************************
	Problem: 1146
	User: wangchenyu
	Language: C++
	Result: Accepted
	Time:5 ms
	Memory:2072 kb
****************************************************************/