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