#include <fstream>
using namespace std;
ifstream in("nrtri.in");
ofstream out("nrtri.out");
int v[803];
int main(){
    int n,i,j,k,st,dr,mid,cate=0;
    in>>n;
    for (i=1;i<=n;i++)
        in>>v[i];
    for (i=1;i<=n;i++)
        for (j=i+1;j<=n;j++)
            for (k=j+1;k<=n;k++){
                st=1;dr=n;
                while (st<=dr){
                    mid=(st+dr)/2;
                    if (v[i]+v[j]>=v[mid] && v[i]+v[mid]>=v[j] && v[j]+v[mid]>=v[i]){
                        st=mid+1;
                        cate++;
                    }
                    else
                        dr=mid-1;
                }
            }
    out<<cate;
    return 0;
}