#include <fstream>
#include<algorithm>
using namespace std;
int n,v[805],i,j,a,k,s,st,dr,m;
int main()
{
    ifstream f("nrtri.in");
    ofstream g("nrtri.out");
    f>>n;
    for(i=1; i<=n; i++)
        f>>v[i];
    sort(v+1,v+n+1);
    for(i=1; i<n-1; i++)
    for(j=i+1; j<n; j++)
    {
        a=min(v[n],v[i]+v[j]);
        k=v[j]-v[i];
        st=j;
        dr=n;
        while(st+1<dr)
        {
            m=(st+dr+1)/2;
            if(v[m]>=a)
            dr=m;
            else st=m;
        }
        if(v[dr]>a)a=st;
        else a=dr;
        st=1;
        dr=i;
        while(st+1<dr)
        {
            m=(st+dr+1)/2;
            if(v[m]>=k)
            dr=m;
            else st=m;
        }
        if(v[dr]>k)k=st;
        else k=dr;
        s+=a-k;
    }
    g<<s/3<<'\n';
    f.close(); g.close();
}