#include <bits/stdc++.h>
#define LMAX 805
using namespace std;
int v[LMAX];
int main(){
    freopen("nrtri.in","r",stdin);
    freopen("nrtri.out","w",stdout);
    int n,no=0;
    scanf("%d",&n);
    for(int i=1;i<=n;++i)
        scanf("%d",&v[i]);
    sort(v+1,v+n+1);
    for(int i=1;i<=n-2;++i)
        for(int j=i+1;j<=n-1;++j){
            int cate=upper_bound(v+j+1,v+n+1,v[i]+v[j])-(v+j+1);
            no+=cate;
        }
    printf("%d\n",no);
    return 0;
}