#include<fstream>
#include<algorithm>
using namespace std;
ifstream in("nrtri.in"); 
ofstream out("nrtri.out");
int n,nr,a[801];
int main()
{   in>>n;
    for(int i=1; i<=n; ++i) in>>a[i];
    sort(a+1, a+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(a[k]<=a[i]+a[j]) ++nr; else k=n;
    out<<nr<<'\n'; 
    out.close(); return 0;
}