#include <fstream>
#include <algorithm>
using namespace std;
ifstream cin("nrtri.in");
ofstream cout("nrtri.out");
int main()
{
    int n,v[805];
    long long ans;
    cin>>n;
    for(int i=1;i<=n;i++)
        cin>>v[i];
    sort(v+1,v+n+1);
    for(int k=3;k<=n;k++)
    {
        int i=1,j=k-1;
        while(i<j)
        {
            if(v[i]+v[j]>=v[k])
            {
                ans+=(j-i);
                j--;
            }
            else
                i++;
        }
    }
    cout<<ans;
    return 0;
}