#include<fstream>
#include<algorithm>
using namespace std;
int a[805],nr,n;
ifstream in("nrtri.in"); ofstream out("nrtri.out");
int main(){
    in>>n;
    for(int i=1;i<=n;++i)in>>a[i];
    sort(a+1,a+n+1);
    for(int i=1;i<=n;++i)
        for(int j=i+1;j<=n;++j)
            for(int k=j+1;k<=n;++k)
                if(a[i]+a[j]>=a[k]) nr++;
				else break;
    out<<nr<<'\n';
    out.close(); return 0;
}