#include <iostream>
#include <fstream>
#include <algorithm>
using namespace std;
unsigned v[803],s=0;
int main()
{
    int n;
    ifstream f("nrtri.in");
    ofstream g("nrtri.out");
    f>>n;
    for(int i=1;i<=n;++i)
    {
        f>>v[i];
    }
    sort(v+1 , v+n+1);
    for(int i=1;i<n-1;++i)
    {
        for(int j=i+1;j<n;++j)
        {
            int x=j+1;
            while(v[i]+v[j]>=v[x] && x<=n)
            {
                s++;
                x++;
            }
        }
    }
    g<<s;
    return 0;
}