n = int(input()) + 2
s = "1" + input() + "1"
cnt = 0
z = 0
renzoku_zeros = [0] * 10 ** 6
renzoku_zeros[0] = 0
renzoku_zeros[1] = 0
renzoku_zeros[2] = 1
renzoku_zeros[3] = 2
for i in range(4, 10 ** 6):
    if i % 3 == 1:
        renzoku_zeros[i] = renzoku_zeros[i - 1]
    else:
        renzoku_zeros[i] = renzoku_zeros[i - 1] + 1
for c in range(n):
    if s[c] == "0":
        z += 1
    if s[c] == "1":
        cnt += renzoku_zeros[z]
        z = 0

print(cnt)