#include <fstream>
#include <algorithm>
 
using namespace std;
ifstream cin("nrtri.in");
ofstream cout("nrtri.out");
int N, A[810], rs, poz;
int main(){
    cin >> N;
    for(int i = 1; i <= N; i++)
        cin >> 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++){
            int sum = A[i] + A[j];
            poz = upper_bound(A+1 , A+N+1, sum) - A;
            if(A[poz] > sum) {
            poz--;
            rs+= poz - j;
            }else  
            rs += poz - j - 1;
        }
    }   
    cout <<rs;
    return 0;
}