#include <fstream>
#include <algorithm>
using namespace std;
ifstream f("nrtri.in");
ofstream g("nrtri.out");
int n,t,nr,m,st,dr,ok,v[808];
int CautBinar(int val)
{
    int st = 1, dr = n, m, ok=0;
    while(st <= dr && !ok)
    {
        m = (st + dr) / 2;
        if(v[m] == val) ok = 1;
        else if(v[m] < val)
            st = m + 1;
        else
            dr = m - 1;
    }
    if(ok == 1)
    {
        while(v[m] == v[m+1]) m++;
        return m;
    }
    else
    {
        m = (st+dr)/2;
        if(v[m] > val)
            m--;
        return m;
    }
}
int main()
{
    f >> n;
    for(int i=1; i<=n; i++) f >> v[i];
    sort(v+1, v+1+n);
    for(int i=1; i<=n-1; i++)
    {
        for(int j=i+1; j<=n; j++)
        {
            t = CautBinar(v[i]+v[j]);
            if(t > j) nr += t - j;
        }
    }
    g << nr << '\n';
    g.close();
    return 0;
}