#include <iostream>
#include <fstream>

using namespace std;

int main()
{
fstream f,g;
f.open("nrtri.in",ios::in);
g.open("nrtri.out",ios::out);
int n,a[801],i,nr=0,j,k;
f>>n;
for(i=1;i<=n;i++)
    f>>a[i];

for(i=1;i<n-1;i++)
    for(j=i+1;j<n;j++)
        for(k=j+1;k<=n;k++)
            if(a[i]+a[j]>= a[k] && a[i]+a[k]>=a[j] && a[j]+a[k]>=a[i])
                nr++;
g<<nr;

}