#include<cstdio>
#include<algorithm>
#define BASE 10
using namespace std;
FILE *f,*g;
int a[3000],i,j,n,m,q;
int main()
{
    f=fopen("nrtri.in","r");
    g=fopen("nrtri.out","w");
    fscanf(f,"%d",&n);
    for(i=1;i<=n;i++)
    {
        fscanf(f,"%d",&a[i]);
    }
   int io=0;
   while(io==0)
   {
       io=1;
       for(i=1;i<n;i++)
        if(a[i]>a[i+1])
       {
           a[i]=a[i]^a[i+1];
           a[i+1]=a[i]^a[i+1];
           a[i]=a[i]^a[i+1];
           io=0;
       }
   }
   sort(a+1,a+n+1);
    for(i=1;i<n-1;i++)
        for(j=i+1;j<n;j++)
          for(q=j+1;q<=n;q++)
          if(a[i]+a[j]>a[q])
            ++m;
          else
            break;
    fprintf(g,"%d",m);
    fclose(f);
    fclose(g);
    return 0;
}