#include<cstdio>  
#include<algorithm>

using namespace std;
  
#define X 801  
  
int main()  
{  
    freopen("nrtri.in","r",stdin);  
    freopen("nrtri.out","w",stdout);  
      
    int a[X],n,i,j,l,sum,sol=0;  
      
    scanf("%d",&n);  
    for(i=0; i<n; ++i) scanf("%d",&a[i]);  
  
    sort(a,a+n);
      
    for(i=0; i<n-1; ++i)  
        for(j=i+1; j<n; ++j)  
        {  
            sum=0;  
            sum=a[i]+a[j];  
            for(l=j+1; l<n; ++l)  
                if(sum>=a[l]) ++sol;   
                         else break;  
        }  
  
    printf("%d",sol);  
  
    return 0;  
}