#include <fstream>
using namespace std;
int n,k,j,i,v[800],sol,ok;
int main () {
    ifstream fin("nrtri.in");
    ofstream fout("nrtri.out");
    fin>>n;
    for (k=1;k<=n;k++)
        fin>>v[k];
    for (i=1;i<=n;i++){
        for (j=i+1;j<=n;j++)
            for (k=j+1;k<=n;k++){
                ok=1;
                if (v[i]+v[j]<v[k])
                    ok=0;
                if (v[j]+v[k]<v[i])
                    ok=0;
                if (v[i]+v[k]<v[j])
                    ok=0;
                if (ok==1){
                    sol++;
                    //fout<<v[i]<<" "<<v[j]<<" "<<v[k]<<"\n";
            }


        }
    }

    fout<<sol;
}