#include <fstream>
#include <algorithm>
using namespace std;
ifstream fin("nrtri.in");
ofstream fout("nrtri.out");
int v[805];
int main()
{
    int n,i,j,k,cnt=0;
    fin >> n;
    for(i=1; i<=n; ++i) fin >>v[i];
    sort(v+1,v+n+1);
    for(i=1; i<=n; ++i)
        for(j=i+1; j<=n; ++j)
            for(k=j+1; v[k]<=v[i]+v[j] && k<=n; ++k) ++cnt;
    fout << cnt << "\n";
    return 0;
}