# include <cstdio>
# include <algorithm>
using namespace std;
int n,i,a[1001],j,nr=0;

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-2; ++i)
        for(j=i+1; j<=n-1; ++j)
        {
            int sum=a[i]+a[j];
            int k=j+1;
            while(sum>=a[k] && k<=n) nr++, ++k;
        }
    printf("%d", nr);
}