#include <stdio.h>      
#include <algorithm>      
     
using namespace std;      
     
int v[801],i,j,n,nr,k,ok;      
     
int main()      
{      
    freopen("nrtri.in","r",stdin);      
    scanf("%d", &n);      
    for (i=0;i<n;++i)      
         scanf("%d", &v[i]);      
    sort(v,v+n);      
    for (i=0;i<n-2;++i)             
    for (j=i+1;j<n-1;++j)            
    for (k=j+1;k<n;++k)            
        if (v[k]<=v[i]+v[j]) nr++;        
        else break;       
    freopen("nrtri.out","w",stdout);      
    printf("%d",nr);      
return 0;      
}