#include<fstream>
#include<algorithm>
#define nmax 808
using namespace std;
int n,v[nmax],sol,mij;
int main()
{
    ifstream f("nrtri.in");
    ofstream g("nrtri.out");
    f>>n;
    for(int i=1;i<=n;i++)f>>v[i];
    sort(v+1,v+n+1);
    for(int i=1;i<=n-2;i++)
        for(int j=i+1;j<=n-1;j++)
    {
        int limD=n+1;
        int limS=j;
           int x=v[i]+v[j];
    while(limD-limS!=1)
    {
        mij=(limD+limS)/2;
        if(v[mij]<=x)limS=mij;
            else limD=mij;
    }
     mij=(limD+limS)/2;
     sol+=(mij-j);


    }
    g<<sol;
    return 0;
}