#include <fstream>
#include<algorithm>

using namespace std;

ifstream fin("nrtri.in");
ofstream fout("nrtri.out");

#define MAX 801
int main()
{
    int i,j,k,n,nr=0,v[MAX];

    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++)
            for(k=j+1;k<=n && v[k]<=v[i]+v[j];k++)
                nr++;

    fout<<nr;

    return 0;
}