#include <fstream>
#include <algorithm>
using namespace std;
ifstream f("nrtri.in");
ofstream g("nrtri.out");
#define nmax 802
#define inf 2000000000
typedef unsigned long long ull;
ull st;
int v[nmax];
int main()
{
    int poz,x,y,i,n,j,k,l;
    f>>n;
    for(i=1;i<=n;i++)
        f>>v[i];
    sort(v+1,v+n+1);
    v[n+1]=inf;
    for(i=1;i<n;i++)
    {
        for(j=i+1;j<n;j++)
        {
            x=v[i];
            y=v[j];
            poz=upper_bound(v+j,v+n+1,x+y+1)-v;
            if(poz<=n)
                st+=poz-j-1;
            else
                if(v[n]<=x+y)
                    st+=n-j;
        }
    }
    g<<st;
    return 0;
}