#include<fstream>
#include<algorithm>
using namespace std;
ifstream f("nrtri.in");
ofstream g("nrtri.out");
int n,v[900],i,j,p,u,mid,nr=0,p2;
int main(){
    f>>n;
    for(i=1;i<=n;i++){
        f>>v[i];
    }
    sort(v+1,v+n+1);
    for(i=1;i<=n-2;i++){
        for(j=i+1;j<=n-1;j++){
            p=j+1;
            u=n;
            while(p<=u){
                mid=(p+u)/2;
                if(v[mid]<=v[i]+v[j]){
                    p=mid+1;
                }else{
                    u=mid-1;
                }
            }
            p2=u;
            p=j+1;
            u=n;
            while(p<=u){
                mid=(p+u)/2;
                if(v[mid]>=v[j]-v[i]){
                    u=mid-1;
                }else{
                    p=mid+1;
                }
            }
            nr+=p2-p+1;
        }
    }
    g<<nr;
    return 0;
}