#include<bits/stdc++.h>
using namespace std;
ifstream fin("nrtri.in");
ofstream fout("nrtri.out");
int n,x,v[888],i,j,t;
int main()
{
    fin>>n;
    for(i=1;i<=n;i++)
        fin>>v[i];
    sort(v+1,v+n+1);
    for(i=1;i<=n-2;i++)
        for(j=i+1;j<=n-1;j++)
        {
            t=j+1;
            while(v[i]+v[j]>=v[t]&&t<=n)
            {
                t++;
                x++;
            }
        }
    fout<<x<<"\n";
    return 0;
}