#include <fstream>
#include <algorithm>

using namespace std;
ifstream in("nrtri.in");
ofstream out("nrtri.out");
int v[801];

int main()
{
    int cnt=0,n,i,j,k,q;
    in>>n;
    for(i=1;i<=n;i++)
        in>>v[i];
    sort(v+1,v+n+1);
    for(i=1;i<=n;i++)
        for(j=i+1;j<=n;j++)
            {   if(j == i + 1)
                {for(k=j+1;v[k]<=(v[i]+v[j]) && k <=n ;k++)
                cnt++;
                q = k - 1;}
                else
                {
                    k = q;
                    while(v[k] > v[i] + v[j])
                        k--;
                    k = max(j , k);
                    cnt += k - j;
                    q = k;
                }
            }
    out<<cnt;
    return 0;
}