#include<cstdio>
#include<algorithm>
using namespace std;
  
FILE *f=fopen("nrtri.in","r");
FILE *g=fopen("nrtri.out","w");
 
int v[801];
int main(){
    int n,nr=0,i,j,k;
     
    fscanf (f,"%d",&n);
    for (i=1;i<=n;++i){
        fscanf (f,"%d",&v[i])
        ;
    }
     
    sort (v+1,v+n+1);
    for (i=1;i<=n-2;++i){
        for (j=i+1;j<=n-1;++j){
            for (k=j+1;k<=n;++k){
                if (v[i]+v[j]>=v[k]){
                    nr++;
                }
                else{
                    break;
                }
            }
        }
    }
     
    fprintf (g,"%d",nr);
     
    return 0;
}