#include<stdio.h>
#include<algorithm>
using namespace std;
int x[800],a,i,j,n,st,dr,gasit,mij,g,k;
bool cmp(int a,int b)
{
    return a>=b;
}
int main()
{
    freopen("nrtri.in","r",stdin);
    freopen("nrtri.out","w",stdout);
    scanf("%d",&n);
    for(i=0;i<n;i++)
    {
        scanf("%d",&x[i]);
    }
    sort(x,x+n,cmp);
    for(i=0;i<n-2;i++)
    {
        for(j=i+1;j<n-1;j++)
        {
            k=j+1;
            while(k<n && x[i]<=x[j]+x[k])
            {
                k++;
            }
            g=g+k-j-1;
        }
    }
                
                printf("%d",g);
                return 0;
}