#include <fstream>
#include <algorithm>
using namespace std;
ifstream f("nrtri.in");
ofstream g("nrtri.out");
int n,i,v[801],nrt,j=3;
int main(){
    f>>n;
    for(i=1;i<=n;++i)
        f>>v[i];
    sort(v+1,v+n+1);
    for(i=1;i<n-1;++i){
        j=i+2;
        while(v[j]<=v[i]+v[i+1] && j<=n){
            nrt++;
            j++;
        }
    }
    g<<nrt<<'\n';
    g.close();
    return 0;
}