#include<fstream>
#include<algorithm>
using namespace std;
ifstream fin("nrtri.in");
ofstream fout("nrtri.out");
int n,i,j,s,v[800],a,b,p,nr;
int main()
{
    fin>>n;
    for(i=1;i<=n;i++)
        fin>>v[i];
    sort(v+1,v+n+1);
    for(i=1;i<=n-2;i++)
    {
        a=v[i];
        for(j=i+1;j<=n-1;j++)
        {
            b=v[j];
            p=upper_bound(v+1,v+n+1,a+b)-v-1;
            nr=nr+p-j;
        }
    }
    fout<<nr;
    return 0;
}