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