#include <fstream>

using namespace std;
ifstream f("nrtri.in");
ofstream g("nrtri.out");
long n,a[810],i,j,k,c;
int main()
{
    f>>n;
    for(i=1;i<=n;i++)
        f>>a[i];
    for(i=1;i<=n-2;i++)
    {
        for(j=i+1;j<=n-1;j++)
            for(k=j+1;k<=n;k++)
        if(a[i]+a[j]>=a[k]&&a[i]+a[k]>=a[j]&&a[j]+a[k]>=a[i])
                 c++;
    }
    g<<c;
    return 0;
}