euler40

汚いな。

L = [9*(i+1)*10**i for i in xrange(10)]

def nth(n):
    n = n-1
    def idx_and_rest(n):
        for i, e in enumerate(L):
            n -= e
            if n < 0:
                return (i, e+n)

    i, rest = idx_and_rest(n)
    
    for j in xrange(10**i, 10**(i+1)):
        size = len(str(j))
        if size > rest:
            return str(j)[rest]
        else:
            rest -= size

print reduce(lambda n, x : n*int(x), [nth(10**i) for i in range(7)], 1)