#include<cstdio>
#include<algorithm>
using namespace std;
int a[801],l,i,j,k,n;
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(i=1;i<n-1;i++)
for(j=i+1;j<n;j++)
      {for(k=j+1;k<=n&&a[i]+a[j]>=a[k];k++);
      l+=k-j-1;}
printf("%d",l);
return 0;}