#include <fstream>
#include <algorithm>
using namespace std;
unsigned int n,v[801],i,j,k,nr,okay;
int main(){
    ifstream in("nrtri.in");
    ofstream out("nrtri.out");
    in>>n;
    for(i=1;i<=n;i++)
        in>>v[i];
    sort(v+1,v+n+1);
    for(i=1;i<n-1;i++)
        for(j=i+1;j<n;j++){
            okay=1;
            k=j+1;
            while(okay==1&&k<=n){
                okay=0;
                if(v[i]+v[j]>=v[k]){
                    nr++;
                    okay=1;
                }
                k++;
            }
        }
    out<<nr;
    in.close();
    out.close();
    return 0;
}