#include <fstream>
#include <algorithm>
using namespace std;
ifstream in("nrtri.in");
ofstream out("nrtri.out");
int main()
{
    int n,i,v[2000],cnt=0,j,k;
    in>>n;
    for(i=1;i<=n;i++)
        in>>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;k++)
    {
        if(v[k]<=v[i]+v[j]) cnt++;
        else break;

    }
    out<<cnt;
    return 0;
}