#include <iostream>
#include<fstream>
#include<string.h>

using namespace std;

int main()
{
    ifstream f("nrtri.in");
    ofstream g("nrtri.out");
    long v[800];
    int i,j,k,n,ok,aux,nr=0;
    f>>n;
    for(i=1;i<=n;i++)
        f>>v[i];
    do{ok=0;
        for(i=1;i<=n-1;i++)
            if(v[i]>v[i+1])
            {
                aux=v[i];
                v[i]=v[i+1];
                v[i+1]=aux;
                ok=1;
            }
        }
    while(ok==1);
    for(i=1;i<=n-2;i++)
        {j=i+1;
         while(j<=n-1)
         {k=j+1;
            while(v[i]+v[j]>=v[k])
                 k++;
            for(int l=j+1;l<k;l++)
            nr++;
            j++;}

        }
        g<<nr;
        return 0;
}