#include <fstream>
#include <algorithm>
using namespace std;
ifstream cin("nrtri.in");
ofstream cout("nrtri.out");
const int nm=805;
int v[nm],n,sl,r,pas;
int main(){
    cin>>n;
    for(int i=1;i<=n;i++)
        cin>>v[i];
    sort(v+1,v+n+1);
    for(int i=1;i<=n;i++)
        for(int j=i+1;j<=n;j++){
            r=0;
            pas=1<<14;
            while(pas){
                if(r+pas<=n and v[r+pas]<=v[i]+v[j])
                    r+=pas;
                pas/=2;
            }
            sl+=r-j;
        }
    cout<<sl;
    return 0;
}