#include <fstream>

using namespace std;

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

int a[30001];

int main()
{
   int n,i,nrt=0,j,k;

   in>>n;
   for(i=1;i<=n;i++)
    in>>a[i];

    for(i=1;i<=n;i++)
        for(j=i+1;j<=n;j++)
            for(k=j+1;k<=n;k++)
            {
                if(k<i+j)
                    nrt++;
            }

    out<<nrt+1;



    return 0;
}