#include <bits/stdc++.h>

using namespace std;
ifstream ci("nrtri.in");
ofstream cou("nrtri.out");
int n,v[802];

int cautarenr(int st,int dr,int a){
int mijval,mijind,rasp;

while(st<=dr){//cout<<st<<" "<<dr<<endl;
        mijind=(st+dr)/2;
    mijval=v[mijind];
    if(mijval>a){
        dr=mijind-1;
    }else{
        rasp=mijind;
    st=mijind+1;
    }




}

return rasp;


}


int main()
{
    int i,j,cn=0,k;
    ci>>n;
    for(i=1;i<=n;i++){
        ci>>v[i];
    }
    sort(v+1,v+n+1);
   // cout<<cautarenr(3,n,6);

    for(i=1;i<=n-1;i++){
        for(j=i+1;j<=n;j++){

           cn+=(cautarenr(j,n,v[i]+v[j] )-j);


        }
    }

cout<<cn;

}