#include <fstream>

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

int s,n,i,j,a[801],k;
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[k]<=a[j]+a[i] && a[j]<=a[k]+a[i] && a[i]<=a[j]+a[k]) {s++;}
            }
    g<<s;
    return 0;
}