#include <fstream>

using namespace std;
ifstream fin ("nrtri.in");
ofstream fout ("nrtri.out");
int n,v[800],ok;
int main()
{
    fin>>n;
int i;
for(i=1;i<=n;i++)
    fin>>v[i];
int a,b,c,ok;
for(a=1;a<=n-2;a++)
    for(b=a+1;b<=n-1;b++)
    for(c=b+1;c<=n;c++)
    if(v[a]+v[b]>=v[c]&&v[a]+v[c]>=v[b]&&v[b]+v[c]>=v[a])
        ok++;
    fout<<ok;
    return 0;
}