#include <fstream>
#include <algorithm>
using namespace std;
ifstream in("nrtri.in");
ofstream out("nrtri.out");
bool comp(int a,int b)
{
    return a<b;
}
int nrtri;
int main()
{
    int n,i,j,p,step,v[810];
    in>>n;
    for(i=1; i<=n; i++)
        in>>v[i];
    sort(v+1,v+n+1,comp);
    for(i=1; i<=n-2; i++)

        for(j=i+1; j<=n-1; j++)
        {
            p=0;
            step=1024;
            for(; step; step>>=1)
            {
                if(p+step<=n and v[p+step]<=v[i]+v[j])
                    p+=step;
            }
            nrtri+=p-j;
        }

    out<<nrtri;
    return 0;
}