#include <fstream>
#include <algorithm>
using namespace std;
ifstream f("nrtri.in");
ofstream g("nrtri.out");
int n,i,v[801],nrt,k,j;
int main(){
    f>>n;
    for(i=1;i<=n;++i)
        f>>v[i];
    sort(v+1,v+n+1);
    for(i=1;i<=n;i++)
    {
        for(j=i+1;j<=n;j++)
        {
            for(k=j+1;k<=n;k++)
            {
                if(v[i]+v[j]>=v[k])
                {
                    nrt++;
                }
                else
                {
                    break;
                }
            }
        }
    }

    g<<nrt<<'\n';
    g.close();
    return 0;
}