#include <fstream>
#include <algorithm>
using namespace std;
ifstream cin("nrtri.in");
ofstream cout("nrtri.out");
int v[801];
int main()
{
    int n,i,s,c=0,j,k;
    cin>>n;
    for(i=1; i<=n; i++)
        cin>>v[i];
    sort(v+1, v+n+1);
    for(i=1; i+2<=n; i++)
        for(j=i+1; j+1<=n; j++)
            for(k=j+1; k<=n; k++)
            {
                if(v[i]+v[j]>=v[k])
                    c++;
            }
    cout<<c;
    return 0;
}