#include <iostream>
using namespace std;
int t(int n){
    int f;
    if(n==1)f=1;
    else if(n==2)f=2;
    else f=t(n-1)+n-1;
    return f;
}
int main()
{
    int s=0,i=1;
    while(s<5000){
        s=s+t(i);
        i++;
    }
    cout<<s;
    return 0;
}

/**************************************************************
	Problem: 1146
	User: chenlingxuan
	Language: C++
	Result: Accepted
	Time:3 ms
	Memory:2072 kb
****************************************************************/