#include <fstream>

using namespace std;


int main()

{
    ifstream fin("nrtri.in");
    ofstream fout("nrtri.out");
    long int n, i, j, a[801], nr=0, sortat, z, aux;
    fin>>n;
    for(i=0; i<n; ++i)
        fin>>a[i];
    do
    {
        sortat=0;
        for(i=0; i<n-1; ++i)
            if(a[i]>a[i+1])
            {
                aux=a[i];
                a[i]=a[i+1];
                a[i+1]=aux;
                sortat=1;
            }
    }
    while(sortat);
    for(i=0; i<n; ++i)
    {
        z=i+2;
        for(j=i+1; j<n; ++j)
        {
            if(j==z-1 && a[i]+a[j]>=a[z])
                ++nr;
            ++z;
        }
        ++z;
    }
    fout<<nr<<" ";

    return 0;
}