#include <fstream>
#include <algorithm>
using namespace std;
ifstream in("nrtri.in");
ofstream out("nrtri.out");
int n,v[805],i,j,k,rez,p,step;
void citire()
{
    in>>n;
    for(i=1; i<=n; i++)
        in>>v[i];
    sort(v+1,v+n+1);
}
void cautare()
{
    for(i=1; i<=n-2; i++)
        for(j=i+1; j<=n-1; j++)
            {
                step=1;
                step<<=10;
                for(p=0;step;step>>=1)
                {
                    if(p+step<=n && p+step>=j+1 && v[p+step]<=v[i]+v[j])
                    {
                        rez++;
                        p=p+step;
                    }
                }
            }
}
void afisare()
{
    out<<rez;
}
int main()
{
    citire();
    cautare();
    afisare();
    return 0;
}