#include <iostream>
#include <fstream>

using namespace std;

ifstream f("nrtri.in");
ofstream g("nrtri.out");

int main()
{
    int n,a[1005]={0},contor=-1;
    f>>n;
    for (int i = 1; i<=n;i ++)
        f>>a[i];
    for (int i=1; i<n-1; i++)
        for(int j=i+1; j<n;j++)
            for (int k=j+i;k<=n;k++)
                if (i+j>k || i+k>j || k+j>i)
                    contor++;
    g<<contor;


    return 0;
}