/*
    code by purplecoder
*/
#include <fstream>
#include <algorithm>
using namespace std;
ifstream cin("nrtri.in");
ofstream cout("nrtri.out");
const int MAX = 805;
int n, v[MAX], ans;
int main()
{
    cin>>n;
    for(int i=1; i<=n; ++i)
        cin>>v[i];
    sort(v+1, v+n+1);
    for(int a=1; a<=n; ++a)
    {
        int c = a + 2;
        for(int b = a + 1; b<=n-1; ++b)
        {
            while(c<=n and v[a]+v[b]>=v[c])
                c++;
            ans += c - b - 1;
        }
    }
    cout<<ans;
    return 0;
}