#include <bits/stdc++.h>
using namespace std;
int ss(int n){
    int r;
    if(n==1)
        r=1;
    else
        r=ss(n-1)+n-1;
    return r;
}
int main(){
    int i=1,s=0;
    while(s<5000){
        s=s+ss(i);
        i++;
    }
    cout<<s;
    return 0;
}
/**************************************************************
	Problem: 1146
	User: lijinkai
	Language: C++
	Result: Accepted
	Time:3 ms
	Memory:2072 kb
****************************************************************/