#include<stdio.h>
#include<algorithm>
using namespace std;
int v[801];
int main()
{
FILE *f,*g;
f=fopen("nrtri.in","r");
g=fopen("nrtri.out","w");
int n,i,j,h,a,b,c,x=0;
fscanf(f,"%d",&n);
for(i=1;i<=n;i++)
fscanf(f,"%d",&v[i]);
sort(v+1,v+n+1);
for(i=1;i<=n-2;i++)
{
for(j=i+1;j<=n-1;j++)
{
for(h=j+1;h<=n;h++)
{
if(v[i]<=v[j]+v[h]&&v[j]<=v[i]+v[h]&&v[h]<=v[i]+v[j])
x++;
else
if(v[h]>v[i]+v[j])
break;
}
}
}
fprintf(g,"%d\n",x);
return 0;
}