#include <fstream>
#include <algorithm>
using namespace std;
ifstream cin("nrtri.in");
ofstream cout("nrtri.out");

int n,u,a[803];
int main()
{
    cin>>n;
    for(int i=1; i<=n; ++i)
        cin>>a[i];
    sort(a+1,a+n+1);
    for(int i=1; i<n; ++i)
        for(int j=i+1; j<=n; ++j)
        {
           int st=j+1,dr=n;
            while(st<=dr)
            {
                int m=(st+dr)/2;
                if(a[i]+a[j]>=a[m])
                    st=m+1;
                else
                    dr=m-1;
            }
            u+=(dr-j);
        }
        cout<<u;
}