#include <fstream>
#include <algorithm>
using namespace std;
ifstream in("nrtri.in");
ofstream out("nrtri.out");
int v[805];
int cautbin(int v[],int st,int dr,int s)
{
    int rasp=-1;
    while(st<=dr)
    {
        int mij=(st+dr)/2;
        if(v[mij]<=s)
        {
            rasp=mij;
            st=mij+1;
        }
        else
            dr=mij-1;
    }
    return rasp;

}
int main()
{
    int n,nrtri=0;
    in>>n;
    for(int i=1;i<=n;i++)
        in>>v[i];
    sort(v+1,v+n+1);
    for(int i=1;i<n;i++)
        for(int j=i+1;j<=n;j++)
        {
            int s=v[i]+v[j];
            int cnt;
            int cb=cautbin(v,j+1,n,s);
            if(cb==-1)
                cnt=0;
            else
                cnt=cb-j;
            nrtri+=cnt;
        }
    out<<nrtri;
    return 0;
}