#include <fstream>
#include <vector>
#include <iostream>
#include <algorithm>
using namespace std;
vector < int > v;
ifstream f("nrtri.in");
ofstream g("nrtri.out");
int a,nr,n;
int cautare(int p, int u, int i, int j)
{
  int m;
  m=(p+u)/2;
  while (p<=u){
      if ((v[m]<=v[i]+v[j] && v[m+1]>v[i]+v[j]) || (v[m]<=v[i]+v[j] && m==n-1))
    return m;
   else if (v[m]<=v[i]+v[j] && v[m+1]<=v[i]+v[j]) {
    p=m+1;
    m=(p+u)/2;
   }
   else {
    u=m-1;
    m=(p+u)/2;
    }
  }
  return 0;
}
int main()
{f>>n;
for(int i=0;i<n;i++){
    f>>a;
    v.push_back(a);
}
    sort(v.begin(),v.end());
    for(int i=0;i<n-1;i++){
        for(int j=i+1;j<n;j++){
           a=cautare(j,n-1,i,j);
           if(a) nr+=(a-j);
        }
    }
    g<<nr;
    return 0;
}