# include <fstream>
# include <algorithm>
using namespace std;
ifstream fin("nrtri.in");
ofstream fout("nrtri.out");
int n,v[801],i,k,j,sol;
int main () {
    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(k=j+1;k<=n;k++){
                if(v[i]+v[j]>=v[k])
                    sol++;
                else{
                    k=n+1;
                }
            }
        }
    }
    fout<<sol<<" ";
    return 0;
}