#include <fstream>
#include <algorithm>
using namespace std;
ifstream cin("ntri.in");
ofstream cout("ntri.out");
int i, j, n, m, st, dr, a, b, nr, mid;
int v[805];
int main() {
    cin>>n;
    for(i=1;i<=n;i++){
        cin>>v[i];
    }
    sort(v+1, v+n+1);
    for(i=1;i<n;i++){
        for(j=i+1;j<=n;j++){
            a=v[i];
            b=v[j];
            st=j+1;
            dr=n;
            while(st<=dr){
                mid=(st+dr)/2;
                if(v[mid]>a+b)
                    dr=mid-1;
                else
                    st=mid+1;
            }
            nr+=dr-j;
        }
    }
    cout<<nr;




}