#include <iostream>
#include <fstream>
using namespace std;
ifstream fin("nrtri.in");
ofstream fout("nrtri.out");
int main()
{
    int n,a[1001]={0},nrt=0;
    fin>>n;
    for(int i=1;i<=n;i++){
        fin>>a[i];
    }
    for(int i=1;i<=n;i++){
        for(int j=i+1;j<=n;j++){
            for(int k=j+1;k<=n;k++){
                if(a[j]<=a[i]+a[k]&&a[k]<=a[i]+a[j]&&a[i]<=a[j]+a[k]){
                    nrt++;
                }
            }
        }
    }
    fout<<nrt;
    return 0;
}