l1 = [int(i) for i in input().split()]
mnln = 0
for i in range(len(l1)):
    if l1[i] == 1:
        ln1 = 0
        ln2 = 0
        t = False
        t1 = False
        y = i - 1
        while(y >= 0) and (l1[i] != 2):
            ln1 += 1
            if l1[y] == 2:
                t = True
                break
            y -= 1
        y = i + 1
        while (y < len(l1)) and (l1[i] != 2):
            ln2 += 1
            if l1[y] == 2:
                t1 = True
                break
            y += 1
        if t1:
            if not t or ln1 > ln2:
                ln1 = ln2
        mnln = max(ln1, mnln)
print(mnln)