#include<iostream>
using namespace std;
#include<stdio.h>
#include<algorithm>
FILE *f,*g;
int a[811],i,j,n,m,q;
int cmp(int a,int b)
{
    return a<b;
}
int main()
{
    f=fopen("nrtri.in.txt","r");
    g=fopen("nrtri.out.txt","w");
    fscanf(f,"%d",&n);
    for(i=1;i<=n;i++)
    {
        fscanf(f,"%d",&a[i]);
    }
    sort(a+1,a+n+1,cmp);
    for(i=1;i<=n-2;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);
}