41 WA

a = [int(x) for x in input().split()]
maxi = 0
dist = []

for i in range(len(a)):
    if a[i] == 1:
        for n in range(i, -1, -1):
            if a[n] == 2:
                maxi = i - n
                break
        for n in range(i+1, len(a)):
            if a[n] == 2:
                if n - i < maxi:
                    maxi = n - i
                    break
        dist.append(maxi)

print(max(dist))