#include <iostream>
#include <fstream>
using namespace std;
long long n,i,a[100001],aux,j,l,r,mid,mx,nr;
int main()
{
    ifstream fin("nrtri.in");
    ofstream fout("nrtri.out");
    fin>>n;
    for(i=1; i<=n; i++)
        fin>>a[i];
    for(i=1; i<=n-1; i++)
        for(j=i+1; j<=n; j++)
            if(a[i]>a[j])
            {
                aux=a[i];
                a[i]=a[j];
                a[j]=aux;
            }
    for(i=1; i<=n-2; i++)
        for(j=i+1; j<=n-1; j++)
        {
            l=j+1;
            r=n;
            while(l<=r)
            {
                mid=(l+r)/2;
                if(a[mid]>(a[i]+a[j])) r=mid-1;
                if(a[mid]<=(a[i]+a[j]))
                {
                    l=mid+1;
                    if(a[i]+a[mid]>=a[j] && a[j]+a[mid]>=a[i])
                    mx=mid;
                }
            }
            nr=(mx-j+1);
        }
        fout<<nr;
}