#include <iostream>
#include <fstream>
#include <algorithm>
using namespace std;
int n,v[800],i,j,st,dr,mid,sol;
int main(){
    ifstream fin("nrtri.in");
    ofstream fout("nrtri.out");
    fin>>n;
    for(i=0;i<n;i++){
        fin>>v[i];
    }
    sort(v,v+n);
    for(i=0;i<n;i++){
        for(j=i+1;j<n;j++){
            st=j+1; dr=n-1;
                while(st<=dr){
                    mid=(st+dr)/2;
                    if(v[mid]<=v[i]+v[j]&&v[i]<=v[mid]+v[j]&&v[j]<=v[i]+v[mid]&&mid!=i&&mid!=j){
                        sol++;
                        st=mid+1;
                    } else if(v[mid]<=v[i]+v[j]){
                        st=mid+1;
                    } else{
                        dr=mid-1;
                    }
                }
        }
    }
    fout<<sol;
    return 0;
}