#include <cstdio>
#include <algorithm>

using namespace std;
int a[801],triunghiuri=0,n,i,i1,i2,i3;

int main()
{
    freopen("nrtri.in","r",stdin);
    freopen("nrtri.out","w",stdout);
    scanf("%d",&n);
    for (i=1; i<=n; i++) scanf("%d",&a[i]);
    sort(a+1,a+n+1);
    for (i1=1; i1<=n-2; i1++)
    for (i2=i1+1; i2<=n-1; i2++)
    for (i3=i2+1; i3<=n; i3++)
    if (a[i1]+a[i2]>=a[i3]) triunghiuri++; else break;
    printf("%d",triunghiuri);
    return 0;
}