#include<fstream>
#include<algorithm>
using namespace std;
int v[800],n;
ifstream f("nrtri.in");
ofstream g("nrtri.out");
int main()
{
    int i,j,st,dr,m;
    int nr=0;
    f>>n;
    for(i=0;i<n;i++)f>>v[i];
    sort(v,v+n);
    for(i=0;i<n-1;i++)
        for(j=i+1;j<n;j++)
        {
        st=j;
        dr=n;
        while(st+1<dr)
        {
            m=(st+dr)/2;
            if(v[m]<=v[i]+v[j])st=m;
            else dr=m;
        }
        nr=nr+st-j;
        }
    g<<nr;
    f.close();
    g.close();
    return 0;
}