#include <cstdio>
#include <algorithm>
#define MAX 810
using namespace std;
int v[MAX],sol;
int main()
{
    int n;
    freopen("nrtri.in","r",stdin);
    freopen("nrtri.out","w",stdout);
    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){
            for(int r=j+1;r<=n;++r){
                if(v[i]+v[j]>=v[r])
                        sol++;
                else
                   break;

            }
        }

    }
    printf("%d\n",sol);
    return 0;
}