#include<stdio.h>
#include<algorithm>
using namespace std;
int v[801];
int main(){
    int n,i,j,k,cate=0;
    freopen("nrtri.in","r",stdin);
    freopen("nrtri.out","w",stdout);
    scanf("%d",&n);
    for(i=1;i<=n;i++)
        scanf("%d",&v[i]);
    sort(v+1,v+n+1);
    for(i=1;i<=n;i++)
        for(j=i+1;j<=n;j++)
        {
            k=j+1;
            while(k<=n){
                if(v[i]+v[j]>=v[k])
                    cate++;
                else
                    break;
                k++;
            }
        }
    printf("%d\n",cate/3);
    return 0;
    }