#include <iostream>
#include <fstream>
using namespace std;
int main()
{
    ifstream fin("nrtri.in");
    ofstream fout("nrtri.out");
    int N,a[100],x,y,z,k=0;
    fin>>N;
    if(N<=150)
    {for (int i=1;i<=N;i++)
        {fin>>x;
        a[i]=x;
        }
        for(x=1;x<=N;x++)
           {

           for(y=x+1;y<=N;y++)
        {for(z=y+1;z<=N;z++)
        if(a[x]+a[y]>=a[z])
            k++;
            }

}fout<<k;
}
}