#include <bits/stdc++.h>
using namespace std;
int num(int n){
    int r;
    if(n==1){
        r=1;
    }
    else{
        r=num(n-1)+n-1;
    }
    return r;
}
int main(){
    int cnt,i=1;
    while(cnt<5000){
        cnt+=num(i);
        i++;
    }
    cout<<cnt;
    return 0;
}
/**************************************************************
	Problem: 1146
	User: luyanchen
	Language: C++
	Result: Accepted
	Time:4 ms
	Memory:2072 kb
****************************************************************/