Euler #71

best, num = 0, 0
for a in range(2, 10**6+1):
    print(a)
    index = int(3*a/7) - 1
    for b in range(index, a):
        if (3/7) > (b/a) > best:
            best = b/a
            num = b
        if (3/7) < (b/a):
            break
print(num)