#include <fstream>
#include <algorithm>
using namespace std;
ifstream cin("nrtri.in");
ofstream cout("nrtri.out");
int n,nr,l[830],s,d;
int caut(int st,int dr,int limst,int limdr);
int main()
{
    cin>>n;
    for(int i=1;i<=n;i++)
        cin>>l[i];
    sort(l+1,l+n+1);
    for(int i=1;i<=n;i++)
        for(int j=i+1;j<=n;j++)
        {
            s=l[i]+l[j];d=l[j]-l[i];
            if(d>s);///imposibil phew
            nr+=(caut(j+1,n,d,s));
        }
    cout<<nr<<'\n';
    return 0;
}
int caut(int st,int dr,int limst,int limdr)
{
    int mij=0,poz1=0,poz2=0,S=st,D=dr;
    while(st<=dr)
    {
        mij=(st+dr)/2;
        if(l[mij]<=limdr)
        {
            poz1=mij;
            st=mij+1;
        }
        else dr=mij-1;
    }
    st=S;dr=D;
    while(st<=dr)
    {
        mij=(st+dr)/2;
        if(l[mij]>=limst)
        {
            poz2=mij;
            dr=mij-1;
        }
        else st=mij+1;
    }
    return poz1-poz2+1;
}