#include <iostream>
#include <fstream>

using namespace std;

ifstream f("nrtri.in");
ofstream g("nrtri.out");

int n,v[801],i,s=0,c=0,j;

int main()
{
    f>>n;
    for(i=1;i<=n;i++)
        f>>v[i];

        s=s+v[1]+v[2];

        for(i=3;i<=n;i++)
            if(v[i]<=s)
                c++;


    for(i=2;i<n;i++)
      {
        s=v[i]+v[i+1];

       /* for(j=1;j<i;j++)
            if(v[i]<=s)
            c++,cout<<i<<" "<<j<<'\n';*/
        for(j=i+2;j<=n;j++)
            if(v[i]<=s)
            c++;
      }
      g<<c;
}