#include <fstream>

using namespace std;

int main()
{
    ifstream in("nrtri.in");
    ofstream out("nrtri.out");
    int i,j,k,cnt=0,aux,v[30002];
    in>>n;
    for(i=1;i<=n;i++) in>>v[i];
    for(i=1;i<=n;i++)
    for(j=i+1;j<=n;j++)
    {
        if (v[i]>v[j])
            {
                aux=v[i];
                v[i]=v[j];
                v[j]=aux;
            }
    }

    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;
}