#include<cstdio>
#include<algorithm>
using namespace std;
int main()
{
    int i,j,*q,v[810],n,a,b,s=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-2;i++)
    {
        for(j=i+1;j<=n-1;j++)
        {
            a=v[i]; b=v[j];
            q=upper_bound(v+1,v+n+1,a+b);
            s+=q-v-j-1;
        }
    }
    printf("%d",s);
    return 0;
}