#include<cstdio>
#include<algorithm>
using namespace std;

const int NMAX = 809;
int n, nrtri, v[NMAX];

int main()
{
    freopen("nrtri.in", "rt", stdin); freopen("nrtri.out", "wt", stdout);

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

    sort(v + 1, v + n + 1);

    for(int i = 1; i <= n - 2; ++i)
        for(int j = i + 1; j <= n - 1; ++j)
        {
            int sum = v[i] + v[j];
            int k = j + 1;
            while(sum >= v[k] && k <= n) nrtri++, ++k;
        }

    printf("%d\n", nrtri);
}