# include <cstdio>
# include <algorithm>
# define MAX (800 + 5)

using namespace std;

int n,i,j,k,nr=0;
int a[MAX];

int main ()

{
    freopen("nrtri.in","r",stdin);
    freopen("nrtri.out","w",stdout);

    scanf("%d\n",&n);

    for (i = 1; i <= n; i++)
        scanf("%d ",&a[i]);
    sort (a + 1, a + n + 1);

    for (i = 1; i < n-1; i++)
        for (j = i+1; j < n; j++)
            for (k = j+1; k <= n; k++)
                if (a[i] + a[j] >= a[k]) nr++;
                else break;
    printf("%d",nr);

    return 0;
}