using namespace std;
#include <fstream>
#include <algorithm>
ifstream fin("ntri.in");
ofstream fout("ntri.out");

int i, j;
int v[800];

int cautbin(int, int) ;

int main()
{
    int n, nr=0, s;
    fin>>n;
    for(i=0; i<n; ++i) fin>>v[i];
    sort(v, v+n);
    for(i=2; i<n; ++i)
    {
        s=0;
        for(j=i-1; j>=1; --j)
        {
            if(v[j]+v[0]>=v[i]) s+=j;
            else if(v[j]+v[j-1]<v[i]) j=0;
            else s+=cautbin(1, j-1);
        }
        nr+=s;
    }
    fout<<nr<<'\n';
    return 0;
}

int cautbin(int st, int dr)
{
    int mijl;
    while(st<=dr)
    {
        mijl=(st+dr)/2;
        if(v[mijl]+v[j]>=v[i] && v[mijl-1]+v[j]<v[i])
            return j-mijl;
        else if(v[mijl]+v[j]>=v[i]) dr=mijl-1;
        else st=mijl+1;
    }
}