#include <iostream>
#include <fstream>
#include <algorithm>
using namespace std;
ifstream fin("nrtri.in");
ofstream fout("nrtri.out");
int a[801];
int main()
{
   long long n,i,nr,ls,ld,mij,ok,s=0,j;
    fin>>n;
    for(i=1;i<=n;i++)fin>>a[i];
    sort(a+1,a+n+1);
    for(i=1;i<=n-1;i++)
    for(j=i+1;j<=n;j++)
    {
        nr=a[i]+a[j];
        ls=j+1;
        ld=n;
        ok=0;
        if(a[ls]<=nr)
        {
            while(ls<=ld && ok==0)
            {
                mij=(ls+ld)/2;
                if(a[mij]>nr)ld=mij-1;
                else if(a[mij]<=nr && (a[mij+1]>nr || mij+1>n))ok=1;
                else if(a[mij]<=nr)ls=mij+1;
            }
        if(ok==1)s+=(mij-j);
        }
    }
    fout<<s;
    return 0;
}