#include <iostream>
#include <fstream>

using namespace std;

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

int a[802];

void binker(int ertek,int n){
    int bal=1,jobb=n;
    while(bal<jobb){
        int kozep=(bal+jobb)/2;
        if(a[kozep+1]<=ertek) bal=kozep+1;
        else jobb=kozep;
    }
    return bal;
}

int main(){
    int n,db=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++){
           if(a[i]>a[j]){
               int temp=a[i];
               a[i]=a[j];
               a[j]=temp;
           }
        }
    }
    for(int i=1;i<n;i++){
        for(int j=i+1;j<=n;j++){
            int ertek=a[i]+a[j];
            db+=binker(ertek,n)-j;
        }
    }
    fout<<db;
    return 0;
}