#include <fstream>
#include <algorithm>

using namespace std;
int v[30005];
int main()
{
    ifstream cin("nrtri.in");
    ofstream cout("nrtri.out");
    int n,i,s=0,j,t;
    cin>>n;
    for(i=1;i<=n;++i){
        cin>>v[i];
    }
    sort(v+1,v+n+1);
    for(i=1;i<=n-1;++i){
        for(j=i+1;j<=n-1;++j){
            t=j+1;
            while(v[i]+v[j]>=v[t] && t<=n){
                ++s;
                ++t;
            }
        }
    }
    cout<<s;
    return 0;
}