#include <cstdio>
#include <algorithm>
#define NMAX 800

using namespace std;

int v[NMAX + 1];

int main() {
    freopen("nrtri.in","r",stdin);
    freopen("nrtri.out","w",stdout);
    int n,i,j,k,t = 0;
    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++) {
        k = i + 2;
        for (j=i+1; j<=n; j++) {
            while (k <= n && v[i] + v[j] >= v[k])
                k++;
            if (k - j - 1 > 0)
                t += k - j - 1;
        }
    }
    printf("%d",t);
    return 0;
}