#include <iostream>

#include<algorithm>

#include<fstream>

using namespace std;

int v[1000];

int main()
{
    int n, i, j, k, s=0;
    ifstream cin("nrtri.in");
    ofstream cout("nrtri.out");
    cin>>n;
    for(i=1; i<=n; i++)
    {
        cin>>v[i];
    }
    sort(v+1,v+n+1);
    for(i=1; i<=n; i++)
    {
        k=i+2;
        for(j=i+1; j<=n-1; j++)
        {
            while(k<=n && v[k]<=v[i]+v[j])
            {
                k++;
            }
            if(k-j-1>0)
            {
                s+=k-j-1;
            }
        }
    }
    cout<<s;
    return 0;
}