n = int(input())
t = list(map(int, input().split()))
k = 0
t.sort()
for i in range(0, n):
    for i1 in range(i + 1, n):
        for j in range(i1 + 1, n):
            if (t[i] + t[i1] > t[j]):
                k += 1
print(k)