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