#include <fstream>
#include <algorithm>
using namespace std;

ifstream f("nrtri.in");
ofstream g("nrtri.out");

int N, triunghiuri, v[801];

int main(){
    f>>N;
    for (int i=1;i<=N;++i) f>>v[i];
    sort(v+1, v+N+1);
    for(int i=1;i<=N-2;++i)
        for(int j=i+1;j<=N-1;++j)
            for(int k=j+1;k<=N;++k)
                if (v[i]+v[j]>=v[k]) ++triunghiuri;
    g<<triunghiuri<<'\n';
    return 0;
}