#include <stdio.h>

int v[802];
int n,i,j,h=1,auxi,s;

int main ()
{
    freopen ("nrtri.in","r",stdin);
    freopen ("nrtri.out","w",stdout);
    
    scanf ("%d",&n);
    
    for (i=1;i<=n;i++) scanf ("%d",&v[i]);
    
    while (h!=0){
          h=0;
          for (i=1;i<n;i++){
              if (v[i]>v[i+1]) {
                             auxi=v[i+1];
                             v[i+1]=v[i];
                             v[i]=auxi;
                             h=1;
                             }
                             }
                             }
                               
    v[n+1]=100000;
                               
    for (h=1;h<=n;h++)
        for (i=h+1;i<=n;i++)
            for (j=i+1;j<=n+1;j++){
                if (v[i]+v[h]<v[j]) {
                                     s=s+j-i-1;
                                     j=1000;
                                     }
                                     }
    printf ("%d",s);
    
    return 0;
}