#include <fstream>
using namespace std;
int n,v[807],cnt=0;
int main()
{
    ifstream fin("nrtri.in");
    ofstream fout("nrtri.out");
    fin>>n;
    for(int i=1; i<=n; i++) fin>>v[i];
    for(int x=1; x<=n-2; x++)
    {
        for(int y=x+1; y<=n-1; y++)
        {
            for(int z=y+1; z<=n; z++)
            {
                if(v[x]+v[y]>=v[z]&&v[x]+v[z]>=v[y]&&v[z]+v[y]>=v[x]) cnt++;
            }
        }
    }
    fout<<cnt;
}