#include <fstream>
#include <algorithm>
using namespace std;
int n, i, j, t, v[805], c;
int main(){
    ifstream fin ("nrtri.in");
    ofstream fout("nrtri.out");
    fin>>n;
    for(i=1;i<=n;++i){
        fin>>v[i];
    }
    sort(v+1, v+n+1);
    for (i=1;i<=n-2;i++)
        for (j=i+1;j<=n-1;j++)
            for (t=j+1;t<=n;t++){
               if (v[i] + v[j] >= v[t])
                    c++;
                else
                   break;

            }
    fout<<c;
    return 0;
}