#include <fstream>

using namespace std;
ifstream fin("nrtri.in");
ofstream fout("nrtri.out");
int v[800],n,a,s,b,c,k;
int main()
{fin>>n;
s=1;
while (s<=n)
    {fin>>v[s];
    s++;

    }
for (a=1;a<n-1;a++)
    {for (b=2;b<n;b++)
        {for (c=3;c<n+1;c++)
            {if ((v[a]<v[b]+v[c]) && (v[b]<v[a]+v[c]) && (v[c]<v[b]+v[a]))
                k++;
            }
        }
    }
fout<<k;
return 0;
}