#include <iostream>
#include<fstream>
#include<algorithm>
 
using namespace std;
int n,a[805],sol;
void Citire()
{
    int i;
    ifstream fin("nrtri.in");
    fin>>n;
    for(i=1;i<=n;i++)
        fin>>a[i];
    sort(a+1,a+n+1);
    fin.close();
}
void Solve()
{
    int i,j,suma=0,p;
    for(i=1;i<n;++i)
        for(j=i+1;j<=n+1;++j)
        {
            suma=a[i]+a[j];
            p=j+1;
            while(suma >=a[p] && p<=n)
            {
                p++;
                sol++;
            }
 
        }
}
int main()
{
    Citire();
    Solve();
    ofstream fout("nrtri.out");
    fout<<sol<<"\n";
    fout.close();
 
    return 0;
}