#include<stdio.h>
#include<algorithm>
using namespace std;
FILE *fin,*fout;
int n,k,i,j,x;
int main()
{
    fin=fopen("nrtri.in","r");
    fout=fopen("nrtri.out","w");

    fscanf(fin,"%d",&n);

    int a[n+1];
    for(int i=0; i<n; i++)
        fscanf(fin,"%d",&a[i]);

    sort(a,a+n);

    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[x])
                    k++;
                else break;
            }
    fprintf(fout,"%d",k);
}