#include <iostream>
#include<fstream>
using namespace std;

int main()
{
    ifstream fin("nrtri.in");
    ofstream fout("nrtri.out");
    int n, k=0, i, a[800], j, m;
    fin>>n;
    for(i=1;i<=n; i++)
      fin>>a[i];
    for(i=1; i<=n; i++)
      for(j=i+1; j<=n; j++)
        for(m=j+1; m<=n; m++)
          if(a[i]<=a[j]+a[m] && a[j]<=a[i]+a[m] && a[m]<=a[i]+a[j])
            k++;
    fout<<k;
    return 0;
}