#include <iostream>
#include <fstream>
#include <algorithm>

using namespace std;
ifstream fin("nrtri.in");
ofstream fout("nrtri.out");
int n,i,j,v[1000],st,dr,mid,s,nr,ok;

int main()
{
    fin>>n;
    for(i=1;i<=n;i++)
        fin>>v[i];
    sort(v+1, v+n+1);
    for(i=1;i<n;i++)
        for(j=i+1;j<n;j++)
        {
            st=j+1;
            dr=n;
            ok=0;
            while(st<=dr)
            {
                mid=(st+dr)/2;
                if(v[i]+v[j]>=v[mid]&&v[i]+v[mid]>=v[j]&&v[mid]+v[j]>=v[i])
                {
                    st=mid+1;
                    ok=1;
                }
                else
                    dr=mid-1;
            }
            if(ok==1)
            {
                nr+=dr-j;
            }
        }
    fout<<nr;
    fin.close();
    fout.close();
    return 0;
}