#include <cstdio>
#include <algorithm>
using namespace std;

int main()
{
    FILE *f=fopen("nrtri.in","r");
    FILE *g=fopen("nrtri.out","w");
    int a,v[800]={0},ok=0,i,j,k,cont=0;
    fscanf(f,"%d",&a);
    for(i=0;i<a;i++)
        fscanf(f,"%d", &v[i]);
    sort(v,v+a);
    for(i=0;i<a-2;i++)
    


        for(j=i+1;j<a-1 ;j++)
            for(k=j+1;k<a;k++)
                if(v[i]+v[j]>=v[k])
                    cont++;
                else
                    break;
    


     fprintf(g,"%d",cont);


    fclose(f);
    fclose(g);
    return 0;
}