#include <iostream>
#include<fstream>

using namespace std;
void quick(int v[], int st, int dr)
{
   int i=st, j=dr, m=(st+dr)/2, pivot=v[m];
   while(i<=j)
{while(v[i]<pivot)
    i++;
 while(v[j]>pivot)
    j--;
 if(i<=j)
{int aux=v[i];
 v[i]=v[j];
 v[j]=aux;
 i++;
 j--;}
}
if(st<j)
quick(v,st,j);
if(i<dr)
quick(v,i,dr);
}

int main()
{
    ifstream f("nrtri.in");
    ofstream g("nrtri.out");
    int v[100],i,j,k,N,ok,aux,nr=0;
    f>>N;
    for(i=1;i<=N;i++)
    f>>v[i];
   quick(v,1,N);
    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;
}