#include<fstream>
#include<algorithm>
using namespace std;
ifstream fin("nrtri.in");
ofstream fout("nrtri.out");
int n,i,j,st,dr,mij,lim1,lim2,cont;
int v[805];
int main()
{
    fin>>n;
    for(i=1;i<=n;i++) fin>>v[i];
    sort(v+1,v+n+1);
    for(i=1;i<n-1;i++)
    {
        for(j=i+1;j<n;j++)
        {
            lim1=lim2=0;
            st=j+1;
            dr=n;
            while(st<=dr)
            {
                mij=(st+dr)/2;
                if(v[mij]<=v[i]+v[j] and v[i]+v[mij]>=v[j] and v[j]+v[mij]>=v[i])
                {
                    lim1=mij;
                    dr=mij-1;
                }
                else st=mij+1;
            }
            st=j+1;
            dr=n;
            while(st<=dr)
            {
                mij=(st+dr)/2;
                if(v[mij]<=v[i]+v[j] and v[i]+v[mij]>=v[j] and v[j]+v[mij]>=v[i])
                {
                    lim2=mij;
                    st=mij+1;
                }
                else dr=mij-1;
            }
            if(lim1!=0 and lim2!=0)
                cont+=lim2-lim1+1;
        }
    }
    fout<<cont<<'\n';
    return 0;
}