#include <cstdio>
#include <algorithm>
using namespace std;
int n,i,a[805],j,sol;
int main()
{
    freopen("nrtri.in","r",stdin);
    freopen("nrtri.out","w",stdout);
    scanf("%d",&n);
    for(i=1;i<=n;i++)
        scanf("%d",&a[i]);
    sort(a+1,a+n+1);
    for(i=1;i<n;i++)
        for(j=i+1;j<=n;j++)
            sol+=upper_bound(a+1,a+n+1,a[i]+a[j])-a-j-1;
    printf("%d",sol);
    return 0;
}