#include <iostream>
#include <fstream>
#include <algorithm>

using namespace std;

ifstream fin("nrtri.in");
ofstream fout("nrtri.out");

int a[810];

int main()
{
    int n,x,y,z,k=0,i;
    fin>>n;
    for(i=1;i<=n;i++)
        fin>>a[i];
    sort(a+1, a+n+1);
    for(x=1;x<=n-2;x++)
        for(y=x+1;y<=n-1;y++)
            for(z=y+1;z<=n;z++){
                if(a[x]+a[y]>=a[z]){
                    k++;
                }
                else
                    break;
            }
    fout<<k<<"\n";
    fin.close();
    fout.close();
    return 0;
}