#include <fstream>
#include<algorithm>
using namespace std;
ifstream f("nrtri.in");
ofstream g("nrtri.out");
int main()
{
    int i,n,a[801],s,c=0;
    f>>n;
    for(i=1;i<=n;++i)
        f>>a[i];
    std::sort(a+1,a+n+1);
    for(int j=1;j<n;++j)
    {
        for(j=i+1;j<=n;++j)
            s=a[i]+a[j];
            for(int k=j+1;k<=n;++k)
            {
                if(s>a[k]) c++;
                else break;
            }
    }
    g<<c;
    return 0;
}