#include <fstream>
#include <algorithm>
using namespace std;
const int N = 801;
ifstream cin("nrtri.in");
ofstream cout("nrtri.out");
int v[N];
const int L = 9;
int main()
{
    int n,i,j,pas,max = 0,r,s=0,k;
    cin >> n;
    k = 0;
    pas = 1 << L;
    for(i=1;i<=n;i++){
        cin >> v[i];
    }
    sort(v,v+n);
    for(i=1;i<=n-2;i++){
    for(j=i+1;j <=n-1;j++){
        k = j;
        while(pas!=0){
            if(k+pas<=n &&  v[k] <= v[i] + v[j])
                k+=pas;
            pas /= 2;
        }
    s += k -j;
    }


    }
    cout << s;



    return 0;
}