#include<stdio.h>
#include<algorithm>
FILE *fin,*fout;
using namespace std;
int main ()
{
   fin=freopen("nrtri.in","r",stdin);
   fout=freopen("nrtri.out","w",stdout);
   int i,n,a,b,c,k;
    fscanf(fin,"%d",&n);
    int v[n+1];
    k=0;
    for(i=0;i<n;i++) fscanf(fin,"%d",&v[i]);
    sort(v,v+n);
    for(a=0;a<n-2;a++)
        for(b=a+1;b<n-1;b++);
            for(c=b+1;c<n;c++)
                if(v[c]<=v[a]+v[b])
                    k++;
                    else break;
    fprintf(fout,"%d",k);
     fclose(fin);
    fclose(fout);
    return 0;

}