#include <bits/stdc++.h>
using namespace std;
ifstream fin("nrtri.in");
ofstream fout("nrtri.out");
int a[805],n;
int main()
{
    int i,j,cnt,k;
    cnt=0;
    fin>>n;
    for(i=1;i<=n;i++)
        fin>>a[i];
    for(i=1;i<n-1;i++)
        for(j=i+1;j<=n-1;j++)
        for(k=j+1;k<=n;k++)
        if(a[i]+a[j]>=a[k] and a[i]+a[k]>=a[j] and a[j]+a[k]>=a[i])cnt++;
   fout<<cnt<<"\n";
   fin.close();
   fout.close();

}