#include<stdio.h>
#include<algorithm>
using namespace std;
FILE *fin,*fout;
int main()
{
    unsigned int n,a[810],i,j,x,k=0;

     fin=fopen("nrtri.in","r");
    fout=fopen("nrtri.out","w");
    fscanf(fin,"%d",&n);

    for(i=0;i<n;i++)
    {
        fscanf(fin,"%d",&a[i]);
    }

    for(i=0;i<n-1;i++)
    {
        for(j=i+1;j<n;j++)
        {
            if(a[i]>a[j])
                swap(a[i],a[j]);
        }
    }


    for(i=0;i<n-2;i++)
    {
        for(j=i+1;j<n-1;j++)
        {
            for(x=j+1;x<n;x++)
            {
                if(a[i]+a[j]>=a[k])
                {
                    k++;
                }
                else
                {
                    break;
                }
            }
        }
    }

    fprintf(fout,"%d",k);


}