#include<stdio.h>
#include<algorithm>
int v[800];
using namespace std;
int main()
{
    FILE *fin,*fout;
    fin=fopen("nrtri.in","r");
    fout=fopen("nrtri.out","w");
    int n;
    fscanf(fin,"%d",&n);
    int i;
    for(i=0;i<n;i++)
    {
        fscanf(fin,"%d",&v[i]);
    }
    sort(v,v+n);
    int nr=0;
    for(i=0;i<n;i++)
    {
        int j;
        for(j=i+1;j<n;j++)
        {
            int k;
            for(k=j+1;k<n;k++)
            {
                if(v[i]+v[j]>v[k])
                    nr++;
            }
        }
    }
    fprintf(fout,"%d",nr);
    return 0;
}