#include <bits/stdc++.h>

using namespace std;
int a[805],n,ans,r,y;

int main ()
{ifstream fin ("nrtri.in");
ofstream fout ("nrtri.out");
    fin>>n;
    for(int i=1;i<=n;i++)
        fin>>a[i];
    sort(a+1,a+n+1);
    for(int i=1;i<=n-2;i++){
        for(int j=i+1;j<=n-1;j++){
            for(int k=j+1;k<=n;k++)
                if(a[i]+a[j]>=a[k] )
                    ans++;
                else
                    break;
        }
    }
    fout<<ans;

}